10% is the absolute minimum and doesn't buy you anything of the house, it just covers the legal and realtor fees.
In the UK, you wouldn’t pay more than a few thousand for a lawyer and associated conveyancing fees, and the vendor pays the realtor (usually in the range of 0.5-1.5% I believe).
We do have stamp duty (tax) which can be substantial eg 15,000 on a 500,000 property.
I swore to my wife that I'm not paying almost 20K to the person giving me a tour of a house.
Seems like selling houses might be a better job than software.