5G doesn't exist yet, so we can only make guesses.  Initially, 5G subscriptions might cost more than 4G, so that the telecom operators can differentiate the different services. My guess is that with time the operators will push the monthly cost for a 5G subscription to the same range as today's subscriptions, since most people don't want to pay more than they are already doing. Hence you will get a much better service for your money.

Huge investments will definitely be needed for 5G. Spectrum will be expensive, irrespective of what kind of bands that will be used. Deployment of new base stations and backhaul infrastructure will also be expensive.

If we compare tariff of 2G, 3G and 4G, it is increasing but download and upload data volume also increasing. In the same given bandwidth, higher data rates are transmitted.

This is mainly due to technology and most of it is implemented in VLSI. Since cost of VLSI is  going down with every year, we expect 5G infra cost will be similar to that of 5G.

Since it is only estimate. we would wait and see, how 5G unfolds.

we expect the cost of tariff of 5G will be same as 4G in course of time.

Cost and Complexity are two main challenges for 5G. For cost of traffic, it is expected that (if we will still have the same operator-user model) users will pay about the same cost of today but they will enjoy higher throughputs and more bits of download/upload. On the other hand, users will have to contribute more to infrastructural costs as lots of gadgets will be in their own premises under their own control. The complexity of 5G is attributed to this transfer of roles from the operator to the customers who will have to posses and run small base stations and backhaul gadgets which raise up the complexity and necessitates that these be self running gadgets and the networks be self organizing networks. The abundance of spectrum together with the increased infrastructural cost on the user might drive a big shift in current operator-users model and future operators can be different (with different roles and ways of generating income) and less centralized than today's operators together with a probable decline (or even wiping out of the traffic (soft) cost. Thanks. @AlDmour.

We expect 5G as an experience rather than technology. At the time of 5G roll of 4G service may offer Much lower tariff , because 5G service may use more sophisticated technology and services

Any how we have to wait and see how 5G rolls over 4G cost wise and servive wise.

We also have to consider how the use case has evolved over time. Think about what you expected your mobile device to do 10 years ago and where you expected it to work.

Compare that to your expectations today.

There are so many factors to consider, each specific to a particular part of the world and the user expectations. I can only throw out some ideas for consideration:

-In the past, a single "high site" could cover a much larger area. Today, with data usage exploding and smaller, low powered devices, the cell radius is smaller. This changes the cost structure for the wireless provider. More sites, smaller sites. The capex and opex may be smaller on a per-unit basis, but the sheer number of base stations has exploded.

- One way to consider wireless infrastructure is the MB/km^2/second the network is capable of delivering. This is really what the service provider is giving to the customers; the ability to sink a certain amount of bandwidth to the Internet per unit area covered. Customer needs and expectations will drive huge variation in the cost to deploy a network. Relatively low capacity per unit area makes for a less expensive network deployment.

- The type of data customers want to put on the network also drives cell radius. Because of the way LTE sets up the uplink air interface, more power can be applied to a narrower SCFDMA signal. The subscriber unit essentially can "reach further", on the uplink but at the expense of data rate. If like most customers, the usage is downlink heavy, it's less of a factor.

- Even if the cost for spectrum went to zero, and all currently practical radio frequency ranges were available, there should be no expectation that cost to provide the service will continue to plummet. It's not like Moore's Law. No matter what the available data capacity per unit area happens to be, the network infrastructure sitting behind that must exist in order to get the traffic somewhere. Routers, optical multiplexers, fiber optic cables.... All of that infrastructure is largely invisible to the consumer, but even as it gets cheaper, the sheer volume of data tonnage on the networks drives capital spending.

- The number of people needed to keep the whole mess working increases, even as the per-unit maintenance/repair requirements decrease. The sheer volume of base stations and supporting equipment across the networks is staggering. It takes an army of engineers and technicians to build and maintain the networks.

-Mike

In summary, Cost of the service is determined by various factors

if energy consumption can be reduced, the operational cost can be minimized:

Solar Powered Cellular Networks

[1] A. Jahid, A. B. Shams, and M. F. Hossain, "PV Powered CoMP based Green Cellular Networks with Standby Grid Supply." International Journal of Photoenergy 2017(8) · February 2017

Link: https://www.researchgate.net/publication/313840103_PV_Powered_CoMP_based_Green_Cellular_Networks_with_Standby_Grid_Supply

[2] A. Jahid, A. B. Shams, and M. F. Hossain, "Energy Efficiency of JT CoMP Based Green Powered LTE-A Cellular Networks." International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET 2017), Chennai, India - March 2017.

Link: https://www.researchgate.net/publication/313421109_Energy_Efficiency_of_JT_CoMP_Based_Green_Powered_LTE-A_Cellular_Networks

[3] A. B. Shams, A. Jahid, and M. F. Hossain, "A CoMP based LTE-A simulator for Green Communications." International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET 2017), Chennai, India - March 2017.

Link: https://www.researchgate.net/publication/313861444_A_CoMP_based_LTE-A_simulator_for_Green_Communications

[4] A. Jahid, A. B. Shams, and M. F. Hossain, "Energy Cooperation among BS with Hybrid Power Supply for DPS CoMP Based Cellular Networks." 2nd International Conference on Electrical, Computer & Telecommunication Engineering (ICECTE), Rajshahi University of Engineering & Technology (RUET), Bangladesh, December 2016.

Link: https://www.researchgate.net/publication/310166355_Energy_Cooperation_among_BS_with_Hybrid_Power_Supply_for_DPS_CoMP_Based_Cellular_Networks

It is always not that easy or cheap to transit from legacy technology to a new one. However, if we define the equation of "5G deployment worthy of it or not ? " by using the sum of Quality of Service (QoS) plus User Experience (speed, latency, accessibility, etc), then divided by the total 5G investment, we might find this value increases over the time eventually. Yeah, we gotta hold the belief, shall we ?

The concept of xG of mobile communications does not apply for 5G.

5G will be a 5G world, users are no more humans (they'll be: things, vehicles, sensors....), no more centric infrastructure, no more specified spectrum, .....and lots of such revolutions.

The major cost shall be that of infrastructure evolution, but very diverse services shall be available, hence, the cost of each service may be less than 4G services, but the overall cost of all services for a user (human, house, vehicle, machine....) shall be higher, covering the cost of 5G rolling.

The answer is yes and no

yes in the sense that if energy consumption can be reduced, the operational cost can be minimized and if free channel slots like the TVWS are used then it can be cheap.

No in the sense that 5G is targeted at millimetre wave region. This will not come cheap. The radio system that will probe and utilized such frequency band will be intelligent, complex in design and will need more power to dissipate in the almost ionizing region of the EMW.