Dear purna
If you looking for a dataset, the kaggle website contains a hug of data.
You can simply crawl data from a eCommerce site like this {https://smartdoko.com/products/mobile-phones } or collect manually. If you go for crawling then python crawling. Look through this website for Python Crawling { https://hackernoon.com/web-scraping-tutorial-with-python-tips-and-tricks-db070e70e071}
You should be specific first, then you can find the required data from the specific vendor.
Since, quality matters by company, same specification of different company will have different quality and price. If you just consider on vendor then there might be the problem of selection bias.
Mobile quality and price, things you are going to compare should be for the similar products. First find the competitor smartphone. Then first determine the base year and identify price and quality. Then try to use panel data to identify change in price due to quantity removing fixed effect of specific company.
Collecting data might not be the problem but being specific in this research is more important.
Source of data:
All the manufactures will publish their model with price in their official website so you can use these official website as the source of data.
There is no any smartphone company in Nepal, so, price of smartphone doesn't depend on local market of Nepal, it is almost world price plus the tax amount. So, you should not consider only Nepal for this project.
Enjoy doing your research.