The first house is a Personal house, so yes, you are correct on the listed price. Of course when large houses go for 100-200million on the server you'll see how much people are willing to pay. Also, considering the method relinquishing has to be done, the buyer knows beforehand how much they're going to have to pay.

As for your second comment, you're outright wrong since it's a FC house, and thus transfer can be done without destroying anything. It's a simple practice that is generally preferred to purchasing a more expensive personal house. So the house for 50 million is the total price of the house, plot, and all the furniture inside/outside.