Hm, my most expensive hobbies...Does raising a kid count???
Cool to see so many musicians and aspiring musicians on here! I'm a music teacher by trade, so overall music makes me more money than it costs me.
I play euphonium (very expensive), acoustic guitar (fairly expensive), bodhran (ditto) and penny whistle (not too bad). The good thing about music as a hobby is that if you get a decent instrument and take care of it, it is a one-time expense that will last your whole life and probably be passed onto your kids and grandkids some day. If any of you need some pointers on how to get started on an instrument, I'd be happy to help get you pointed the right direction.
Nice to hear from some runners on here, too. Trail running is one of my great joys, but not an expensive hobby as I really just need a pair of shoes and a water bottle (and I usually don't even take a water bottle)
@robmcd I dream of doing an ultra, but I have to content myself with 10ks and half marathons. I figure a half marathon in the Wind River Range is good enough.
Probably my most expensive hobby is primitive archery. I'm learning to make bows, and I've been making my own arrows for years. Bow staves (good, straight-grained split tree trunks) are fairly expensive, even though I have friends that collect them for me and I usually only pay shipping. I'm learning to use more local materials, so the time cost (and satisfaction!) will increase but the monetary cost should eventually reduce to almost nothing. Hopefully.