the loud snap then a lot of bad words

just after building a little dirt jump in by back yard i go up the street to get some speed I HEAR THIS LOUD SNAP thinking my chain just fell off But i look down and SEE MY REAR DERAILER INSIDE MY WHEEL (WTF) and this is were i should stop telling my story
the pics explain a lot
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And now i am just wondering how much a rear derailer is going to cost
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whats missing here
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it looks like the drop out can be replaced
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NO Riding for a while (this Sucks)