Why so many e-shops offer HUGE discounts if order is paid in crypto?

10%, 15% sometimes 20 and even 25% off entire order if you choose crypto as a method of payment! Where's the trick? I just consulted my accountant today who has extended knowledge in business and crypto accountability and sellers are taxed the same rates than with orders being paid with regular money... then why does sellers push customers to pay crypto offering such discounts ? I might have an idea though, not declare those sales to the tax authorities because hardly traceable? So 100% gain? That's the only explanation I see so far. Anybody having another idea? Cheers!