Hmm, well bought a new bike last month so that’s pushed the total up by a bit 🙄 I’ve got three active bikes (plus one that’s in limbo) and mostly it’s a matter of servicing/maintenance costs.
This year’s big spends have been getting lightweight bikepacking kit so although bike related it’s not actually bike parts – things like lightweight, compact sleeping bag, sleeping mat. In part these have been replacements for some very old kit I’d left over from my climbing days, things have moved on.
Is biking/mountain biking expensive? If you can’t afford it then yes it is, but in absolute terms there are a lot of expensive hobbies/sports around: anything motorsport related; sailing (especially ocean going rather than inland water); equestrian sports.