Sewing Hobby on Wedding Registry?

It's common for people to put a $400 KitchenAid mixer on their registry, even if they're not avid bakers, so I don't see why not. I would discuss it with your FH and make sure that's the one expensive item you want to put on there.

I would put it on. Most sites have options for people to split the cost of an item.
Honestly my FH and I live in one of those 'tiny houses' so with our 224 sq/ft we already have everything we need. So our wedding registry is made up primarily of recreational items such as fishing gear. That's our main hobby and I know it will get used by us.

We put a sewing machine on ours. It wasn't quite so expensive (only $99), but I sew recreationally and won't be doing anything too elaborate. Once I start making more clothes (and have more time), I can't wait to use it more!

I think you should put it on!! Even if nobody buys it often you get a completion coupon after you close the registry so if anything you can use the coupon and buy it yourself

I think it's fine! As long as you have plenty of gifts in lower price ranges. Amazon also allows people to "group gift" so that would give 4 people the option to each spend $100 for you!