Have a look on lowendtalk.com there are regular offers for cheap storage servers (I'm currently running a 2 Tb 6G 2CPU VPS that I got for $80 a year). Also if you just want to attach storage to an existing VPS you could get a storage box from hetzner. Other alternatives exist, e.g. Ionos.de had (has?) a nextcloud offer with 2TB for 10 euros a month.