Real Estate agents....can u explain land transfer tax?

Bad enuf with over inflated real estate prices, I need a garage extension and the permits, fees, taxes, material it's ridiculous. I bet I'll be $25-30k adding 3-400 sq ft. So we look for "something else" and the LTF is out to fn lunch. Let alone the house price.
Yep I’m trying to build an entire house… it’s nuts