I'm getting a very small kitchen extension (hopefully), no units or anything like that, 3 walls and a roof, two windows, the usual plumbing and electrical, couple of roof windows and I have 4 quotes, all around 25k which is fine, I expected that but it's nowhere near a finished price and I'm not in a major city or anything. All are small local builders and I expect to have to spend another 10k anyway to actually finish it. I'm not even going to put in a new kitchen as such, just fit out the extension bit with something that suits the existing kitchen, bit I'm hoping to build is roughly 6 ft x 15 ft give or take.
I'd be surprised if you got a finished price of 25k.