A VM with BGP session can be had for 10€ or less — add some free WireGuard and you could use your own "static" IP prefixes! (Or just get an even cheaper VM without BGP and use the fixes addresses assigned to it for tunnelling.) You'll likely trade a bit of latency for money, but wellp …
Or just go with DynDNS for basically 0€, get the (likely) low latency, and accept a few minutes of downtime on address changes. Also a very valid option, and a cheap one!
