Assuming you have wired connections to begin with.

I live in an older apartment complex which was build in early 70s and there is only very poor copper connection, so I can get at most 8Mbs in through that. Slow speeds have forced me to look for alternative solutions and 4G LTE is the way to go here, it costs just shy of twice my old setup, but I get 80-100Mbs in and out, which is 10 times as fast, but being on 4G means I can need my router/modem/thing to be 4G enabled and while my main PC is connected to that router via Ethernet most of my devices use WLAN (things like chromecasts, phones, tables, and laptops).

Maybe I'm in very tiny minority here, but just saying things aren't always as simple.