I had a rough quote recently, all in it was near 100 but the actual extension part came to 25k. Glass/doors can range from 1000 to 25000 or more. Same with kitchens. My pals renovated recently and they budgeted 65k and I think it came in at 130k in the end. It’s a terrifying can of worms.
Dep on size and spec expect no less than 50 and prob closer to 70. Could easy go way higher too.