Used to pay 3€/mo for 15G (moderately generous, compared to public offerings). I upgraded to 50G (+5€, 8€) during last winter, due to video calls and blackouts (networking, also ISP's stations, run around 15m afterwards).
A competing SP started offering unlimited (as the first public and not insanely-priced), with a half year of half the price, and now at 15€/mo.
Still, unlimited wasn't offered to me, I got offered 30G, 50G, and 110G as alternatives.
50G is enough for me to not worry about. In two cases, with 2-3 events of many-many-hour video streaming or more likely forgotten large syncthing change, I've run out, and had to buy extra (dual-sim, burner).
Still, I bring out yet once again: having the peace of mind to not care about mobile data is gold. To me, 5 and 15G are practically the same.
Some apps like to play dumb (by draining or not working) if they don't have a pipe to suck.