The only "dumb" part of your OP is thinking your bass "broke." Short of going full Pete Townsend/Kurt Cobain on your instrument, there's very little that could have been done to it that can't be repaired for less than $300 - and actually, even if you had, depending how many pieces it splintered into, $300 just might cover the repair at the right shop. (E.g. a lesser known repair guy looking for a chance to show off his chops).
To respond to your question, though, if you just want to buy an 8 string bass because you think it would be fun to play on, go for it. shag the haters.