Solend uses Pyth, and Switchboard as a backup.
Since Solend uses Pyth and Switchboard, it needs a feed from one in order to list an asset.
TL;DR it's only expensive the first time you use Solend.
Nope Finance is a project that Solend acquired in June. Nope Finance already had the NOPE token, so Solend offered a conversion to bring the Nope community into Solend's.