A company can be a registry for a tld, like how Google owns the .app tld. That is different than a registrar, like godaddy, who resells the names in namespaces provided by registries. The registries set the price for that tld and other things like requiring .app namespace to be secure, so you need HTTPS and an SSL certificate for your website to load on most browsers. Due to these SSL requirements, domain forwarding isnt supported. another example of requirements set by a registry is the .AI namespace which is more expensive by default (over $125 a year last i looked)and requires a minimum of 2 years when you register.

Registries also charge more for names they think are worth more. So if you see a premium .app name that cost $2,000 per year, that is because the registry (Google in the case of .app) decided the name was valuable (probably because its a short common noun) and they want a lot more per year for it. Ive never heard of this happening after someone already had it for cheaper, so no rug pull type situations.

As for why some names renew for more than when you first get them, its a strategy for registrars (not registries) to attract new customers. Companies give items away at a discount or loss to get you into their ecosystem and then make profits at renewals. It’s like getting a free smartphone from a phone company and then paying more for the service than if you had owned the phone and not got it free.

That's just a limitation on some registrar. Domain forwarding absolutely does work on .app; you simply need to configure an SSL certificate on the web server serving the redirect for the forwarding.