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You got me curious so I opened both games and, what do you know, you were right:
http://goo.gl/rojhfi
They are indeed the same game, maybe with minor modifications. And the engine is, indeed, box2d...

I say 200 bucks are fine for coding alone, I mean who would even want to code it for under 200 bucks? School boys? On the other hand, I think this game needs another 1000 for better artist to re-do...