I purchased Microsoft lumia 640 from amazon worth 8000. It is a very good windows phone and has a lot of functionalities.
The main advantage of windows phone over android is guaranteed update and battery backup. It is a very slim and supports a lot of functionalities. The main disadvantage of a windows phone is the availability of apps. But I preferred it over lumia 540 because it just has a 5mp front camera whereas the lumia 640 has glance screen, gorilla glass and many other features even if both of them are of the same price.