I think there's a work surface under all my stuff
But seriously, I agree with watching for sales and visiting thrift shops.
If it's in the budget, however, I would look into the Sew Ezi tables. I had heard about them, but saw them in action at a quilt retreat. I got the portable, and the design is really well thought out. I sew in the dining room, so it's nice that the table folds up and I can put it under a bed when I need to. Depending on what I'm working on, I can position it so my dining room table is in front of or on the left side of the machine. It had been years since I sewed on my mom's cabinet machine and I was amazed at how much more pleasant it was to sew when the machine bed is even with the table height.
http://www.seweziusa.com/our-products.html