909% mark up groupon vs cash proces

I hope you haven't bought the Groupon for Tattoos by Mr.Dee's. I inquired the price of a script I wanted tattooed. They asked if it was cash or voucher (groupon). The cash price was R550 and the groupon price was R150 per letter. For the script I wanted that would be R5550 for the exact same words. That's a 909% mark up just for using a voucher that should make the tattoo cheaper. That's bad business practice. Hope no-one has fallen into that trap.