Then buy a house that isn't plastered and go without or DIY... no one is forcing you to buy a house that's finished!
Of course in reality, you're barely going to save anything, the few hundred £ extra it costs to plaster the walls pales into insignificance compared to everything else when it comes to the cost of the house. As already mentioned by Greebo above, the cost of the plot is going to be one of the biggest factors.
Anyway, I give up. Good luck finding anyone that's bothered to actually go to college/university in your communist utopia where everyone gets paid the same regardless of skills or experience. How much a plasterer costs is going to be the least of your worries when you get sick or injured and there are no doctors.
Communism doesn't work. People are greedy and selfish by design.
No way I'd be doing a skilled job for same moneys as low skill job