Anything is possible, is the simple answer, but there is a method that you can use to reduce the average price that you pay for replacement double glazed windows
Initially you should gather a number of written (fully fitted) double glazed windows prices from at least 3 or 4 reputable companies (more if you can) and then take a good look at them ensuring that they are all based on a “like for like” pricing and content basis.
Go through the quotes and find 2 things:
1) the company you prefer
2) the lowest price
Once you have these things call the installer you prefer and tell him / her that if they give you a better price that they stand a very good chance of getting your order.