Is it tacky to ask for $ in lieu of a wedding registry?

Going to a friend’s wedding who is asking for cash instead of gifts. They have a condo and have pretty much all the essentials. They have a small registry but 90% of the items are priced $600-$2000 each. I’m already spending $1500 on the bachelorette, and $300 for wedding outfit/small personal gift/bridal shower gift. So their wedding has already cost me almost $2k and I’m not even a bridesmaid getting my dress covered lol. Anyways, is it tacky to ask for cash?