Since you seem to have most everything that one would need, how about finding a charity that needs some help or a family who are in need.....and give something to them.

Since you would be the donor, it would be like spending it on yourself...would buy you peace of mind and that's a wonderful feeling.

Fabric! Fabric! Fabric! A quilter can never have to much fabric. :0)
You don't have to feed it, you don't have to paint it, it justs lays there waiting to become a quilt.

I just bought a singer featherweight 221 and love it!

I would absolutely go for the presser feet: The leather foot that lets you do curvy lines, the needle punch for free motion needle felting, the circle attachment that Bonnie Lehman uses... It wouldn't take many to use up $250. Or buy some really good gourmet chocolate! :-))

Choclate is a great Idea.................also spoil yourself with great thread......personally i would go straight to my LQS and buy big cones of the basic (white, off white, black,gray,tan) and the smaller cones of everything in AURIFIL

or join Superior thread of the month club for King Tut.....I dream about this thread, really i do :o

I would say pay off a credit card. After that go to LQS and spend the left over.

What about one of the fabric cutters? A sizzick? Personally, I'd love something that accurately cuts strips.

Does the card expire? If not and donanting don't appeal to you, then save it until you find something you need.
Of course it might get pretty dusty since you have a pimped out studio already.
If it was me I'd buy batting at 1/2 price, always need batting.

I think I would go with a whole roll of batting. Do you have the rulers that have the sharpening edge on them? I don't yet but I think they would be great.

Shelving and the "boards" to get my fabric displayed and easier to see and make good use of. If any thing left over..... organizational things to keep my sewing room, can't call it a studio yet, in better order.