What is your "inexpensive" hobby that turned out to be expensive/ you gradually invested lots of money into?

Dog training/sports.

Here I am thinking "I need to get more active and it'll be fun to do stuff with my best bud Link" (Link is a 4 year old golden retriever)

Starts with basic training obedience classes, no biggy. Then they offer Rally classes, which is basically obedience plus some fun stuff, cool, I'll take that class. Oh, I can get a cool title for him? Sure, we already trained him, why not! Ok he needs 3 successful runs, and each run attempt is $25...? k...

Rally Novice acquired...fun but... Was that really worth 150 for the class + $75 for the three runs? ...sure whatever

Ooooo agility sounds fun! Let's do that! $150 for a 6 week session, that's not bad! 6 months and many sessions later + buying practice equipment... I'm officially poor. My dog is a happy boy, and I'm more active, but FML this is a rabbit hole lol

We're having a lot of fun, and my dog is a happier more obedient boy, but man was I not expecting the crazy expense. Those people with the dogs that have a bazillion titles and letters after their names? They've spent a literal fortune on that dog. It's absolutely mind boggling.