This is heavy question.Cost depends on the region wher you work and it can vary a lot from coutry to coutry.For one case where my Department prepares Design for slope protection in compex geological and field conditions, based on a market analyses and data about cost from companies, we prepare diagrams of costs for several typical protection types. This can be a way for fast estimation of cost for  similar method of rock protection with a system of rock bolts combined with wire mesh and schotcrete. The article in Macedonian language is on my profile on a research gate and it is for case  of acces road to arch dam Sveta Petka in my country. I dont have data about types of soil improvements, but I believe that similar diagrams can be prepared. If necessary I can send you this article just to see the idea.

I think the best way is to participate more engineering projects and accumulate the data.

You can check it locally by contractors