I agree with what you're saying Chalky,,but one thing that drives prices up is demand at the time .
A top dj plays it,everyone wants one (cos they've already told folks "Its at home".. ),,suddenly that "cheapie" isnt so readily available as first thought.
Problem is its just the flavor of the month - so back under the bed it goes with the rest of the mountain.
Burnt my arse on the bedroom light last night,the mountains that high.!!
As for grading,its very hit and miss.Some sellers are better than others,or more honest,sometimes the grading isnt clear cut.Some buyers want more for their money.
Paying over the odds happens.The price may not be right,but you have to strike while the money is there,and hope you dont get stung too much,when you sell on.
Sherpa Tensing.