marketing costs alot of money. If you want your property to be featured in the Big mags like Lands of Texas and Farm & Ranch, those ads arn't cheap, I can see someone asking for 7%-8% for a smaller deal.
I don't think WP does any specific advertising for your property unless you choose the auction route and then you have to pay a fixed fee and some back-end for the marketing. WP has a great website and TV show that reach a huge audience, that is their main benefit over a local agent and listing with MLS. That's what you are paying for. I think it still comes down to how hard the agent works for you, a local agent with local contacts plus MLS or a distant agent trying to catch out of state buyer. FYI at least area I'm in the current land owners are flush with money last few years from price of beans etc. Supposedly most that come in from out of town with big pockets get beat by locals with even bigger pockets, I snuck through.