Apple has much better support for their phones, you can get iOS 17 on Xr which was released in 2018. On the other hand pixel 3 which was also released in 2018 lost official support with android 12 but of course in android you could just flash a custom rom and call it a day. So I don't think it's fair to say you need to upgrade every "couple" of years given the average user probably upgrades every 3-4 years regardless if they use iOS or Android.

The cost will be spread out on an instance by instance basis due to which the cost per user will be low and if not they can also host their own instance which doesn't cost a lot. If it's something around $5 a month I wouldn't mind paying to support a service I plan on using everyday.

According to a twitter engineer this is temporary Source: https://twitter.com/AqueelMiq/status/1674843555486134272

Man i really hope Reddit dies and people move onto decentralized networks, in time I'm sure we can figure out how to index a decentralized network for search engines completely replacing Reddit.