I have a little info on these but some of it may be off.
M.A.R.S Is a toyline by happy kid toys. Most of their bots do not transform but they do have a line called cybertronix that transform. I think this is what you were talking about but I'm confused at the big butt price comment as cybertronix are only $10 at retail. They can sometimes be found at Walgreens but mainly from my experience pop up in Wal-Mart and family dollar. Family dollar seems to be ahead in releasing new figures as Wal-Mart is still stuck with the first couple waves.
These toys are pretty good for their price and size I think. The first 2 waves were not so great but the 3rd and 4th are better.
These are leader size or slightly smaller. The first 2 waves featured a bulldozer, cement mixer, and 3 cars (blue, red, grey). The 3rd wave was a blue stegosaurus, red trex, and a yellow dragon (who's name on the box is listed as goldy dragon). The 4th wave is a tank and jet.