Coffee. It CAN get extremely expensive, but importantly the expensive parts can be re-used for decades, and also there's a bit of a bend point in value for the hobby.
Once you get a $150 really good grinder and start grinding whole beans every day, you've gotten 40% better. Then maybe a Chemex or Aeropress for $50 and a weight scale for $20 and you're another 30% better. After that...it's easy to spend $300+ at a time on better equipment or getting into espresso but each thing is like a 5% improvement. You'll notice, but if you don't have much money, it's not really worth it.
And the beans SEEM like they're getting expensive but a bag gets 2 weeks of coffee for me, $20 for really nice beans just isn't that much per cup.