While I agree that money should be more plentyfull if you get really far, it isn't as big of an issue. It is how the game is meant to be played and I'm fine with it. I have been playing on and off for a couple of days whenever I have some free time. It's a decent timekiller.
The lack of explanation is for me however the biggest flaw in this game. The cars don't have any stats, so you don't know their flaws or strengths, if they have any. The comments imply that they do. Same goes for the upgrades and those 10K bonuses you can buy once in a while. I scoured the comments because I didn't know how to get the overdrive, or the slams.
Secondly, I have this feeling that missions aren't always counted correctly. I noticed several times now that even though I did 20 flips, the 20 flips mission isn't completed. The same goes for several "jump X meters"
However, the lack of explanations is the biggest issue. If you could add/clarify this, it would make for a perfect game.
 "Extreme Road Trip 2"){kind=icon}
 "The Fabulous Screech"){kind=icon}
 "SandTest"){kind=icon}
 "Abduction!"){kind=icon}
 "Cosmic Crush 2"){kind=icon}
 "The Gun Game"){kind=icon}