You said you wanted a secure workshop for your alchemical studies, storage of herbs, your booze collection and such
the set prices for wood buildings are as such (wood a couple inches thick)
small 400sq ft 48gp
medium 800 72gp
large 1800 108
great 3600/2floors 240
grand 9600 sq on 3 floors = 450
Stone has the same buildings sizes (or something in between can be calculated.)
2 ft thick walls
prices @
3200
4800
7200
16000
30000
Stone was calculated at 1.6x base price, wood and brick 1.2x base because they are sourced locally.
22,800 gp
I'm suggesting an in between quality of 1 ft thick, double or triple brick houses at the 1/2 the stone price. I still think brick should be cheaper per cubic foot than finished stone but I can find no references to compare, so we'll just go 1/2 thickness walls are 1/2 price
1200
1800
2700
6000
11400
Likewise there should be a wadle and dob version of a the hut availabe very cheap.
You can also reduce the price somewhat by doing some of the labour.