Lynn,
I hope you can convince him to give her the cash to buy what she wants, and make sure he gets creative in how he wraps and presents it to her. I'd use six, 100 dollar bills in six silly presents (package of needles, seam ripper, spool of thread, etc.).
With the cash, she can find great deals and sales to buy anywhere and may even opt for a used machine off of Craig's list or from a dealer, that cost much more new. I got my $1400 Bernina at a yard sale for $500. Some of the sites offer free shipping and financing, so she just might want to use the $600 as a down payment on her dream machine.
He is a great husband!
Diane