Sherrill's %150 price crusher saves me plenty, even over the local arborist supply store, only down side is they dont have free shipping like WesSpur.
Do you prefer leg straps or a seat? Some saddles as im sure you noticed can be changed out to have either or. I have the Butterfly II and love it. Super light, very adjustable,good back support, good places for hardware (though it lacks attachment points 4 them, in turn keeps the over all weight down I guess).
If $500 is your budget then go on and buy the TreeMotion, thats what id get given your allowance. All the above suggestions are great ones. I like the buckingham saddles but straps and floating D's are out dated and non-replaceable in most cases. So the longevity of the highly adjustable newer saddles is definitely a plus!