Hasbro mentioned that Classics was cancelled forever so they released the remaining seekers Thundercracker, Thurst and Dirge as Botcon exclusives. Because a lot of people wanted to complete their Classic collection there was a bit of a frenzy to get them driving prices up to ridiculous amounts for each figure. Not long after that, they announced that there would be a Universe 'Classics 2.0' line in which they could have potentially released those characters and therefore make them more accessible to all fans. Since they cannot release exclusive toys into mainstream retail, releasing those characters for Universe was out of the question specially when several fans had already forked out US$250-300 per figure.
It hurt a lot more when much cheaper (but still expensive by retails standards) Henkei version of said characters were released including a fully remolded Dirge as Botcon Dirge was just a repaint of Ramjet.
The hardest figures to Track down from the Dawn of Futures Past set are:
Megatron - The rarest and by far the most expensive figure, can go for $500
Waspinator - Came with Megatron but by itself it would likely be at the $100-$150 mark.
The others balance out fairly well at $100-$150