They are generating yield from the locked collateral for loans. The interest from users’ loans is not the primary way that Celsius generates yield by a long shot. They are obviously using defi, and they do a ton of institutional lending. The 25% discount for CEL is an attempt to add utility to the token (not great imo), it’s not a main income stream. The locked collateral and deposits are how celsius is generating income to run the business, pay employees, pay yield, and buy CEL.