I traded my services as a flight instructor for a pile of rock and crusher fines. The deal was free instruction for all the rock and fines I could haul. I hauled a bunch of it too. Enough rock to build my house and coat my road and airstrips with fines, and I still have a big pile of rocks left over. The student pilot received about $2,100 worth of flight instruction towards his private pilot license. Yep, he passed first rattle out of the box.