It's not $2 per month to the end user. Reddit wants to charge the
wholesaler $2.50 per month. The developer needs to keep the lights on, so they need to charge more than that. There are server costs for Apollo, tech support, accounting, refunds, etc. Apple and Android take their 15-30% cut. The developer indicated a break-even price of between $5-$7. I'd be perfectly happy to pay $2/m for Reddit, and I'm happily donating to kbin.social to keep them running. The interface is much better than Reddit. Despite the lack of funding, their incentive is to create a great user experience.
It's important to remember that that $2.50 Reddit is charging isn't their cost. They're a business and they're baking in a health profit margin on that. The actual cost to them is a fraction of that, though of course they will never disclose the actual amount.
You might recall that back in 2000 we didn't have Reddit. It was lots of little forums hosted on machines in basements and with relatively cheap online hosts. Lemmy and Mastodon allows us to do that again, but this time, they're all connected together. This distributes costs across hundreds of thousands of people, instead of trying to make one giant platform the only choice.