The fee for listing your house is also done IRL. For example, in Etsy, you pay I think $1 for them to enlist your items and then they take a small fee if that item was sold. To counter this, all the seller needs to do is incorporate the expense to the sales price.
I'm not really sure why you gave that example about the house because if you also use sites like real estate websites, what Splinterlands is doing, they are doing it. The site will include a fee for listing, and the agent who will do the documentation, etc will get the fee for selling/buying the house.
RE: Market Listing Fees & Expiration