Thomas Shey
Legend
Are TTRPGs more expensive than cooking/baking? (How do you price this? Solely on ingredients? On pans and mixers and pots? Do you factor in the oven/stove? The cost of renting/buying the house?)
I'd say the ingredients and the cooking implements. Most people aren't going to buy a custom stove just because they like to cook (though its not unknown). That said, you can dump some big money in those two components pretty fast. A single Hexclad pan goes for more than $120.
Are TTRPGs more expensive than pets? (Probably not. Pets plus food plus vet bills plus toys get expensive in a hurry).
Certainly not dogs and cats. And that's not assuming (as might well be with a serious hobby) that you get into show animals...
Are TTRPGs more expensive than outdoor activities? (Probably yes for hiking where the only costs are shoes, water, and maybe sticks. But probably not for anything else - skiing, boating, backpacking, camping, mountain biking - all of these will cost you a lot more).
Even hiking can have some serious ancillary costs if you live in a large city and want to get there.
Are TTRPGs more expensive than DIY Arts & Crafts? (Probably yes on an individual craft basis, but probably not if you're crafting weekly or biweekly).
The crafty people I know would laugh at this.
Are TTRPGs more expensive than Gardening and plants? (This one's a push depending on how much gardening you're doing and how expensive your plants are. If you get hardy perennials as a one-time expense and just keep them up, TTRPG is probably the more expensive bet. If you're re-planting your garden every season with flowers to match the holidays, it's gardening).
On the other hand, no one who's just doing the maintenance on perennials probably considers it their hobby.
So... I think the answer is "it depends on exactly what hobbies you substitute for TTPRGs... but TTRPGs are probably not really all that expensive a hobby." Of course there are some versions of hobbies that will obviously be cheaper than TTRPGs (Uno cards, jogging, reading), but most common hobbies look like they would be a push with TTRPGs (board games, baking, arts & crafts) if not wildly more expensive (especially travel and cars, but even playing poker with your buddies might be more financially stressful).
And like I said, seriously don't underestimate most crafts.