I looked into GrubHub to do online ordering for my mothers deli, after seeing the roughly 25% fee I can safely say that many small business will look elsewhere... eventually.
We're a small startup out of Charlottesville, VA, but we'd love to help out your mother if we can! Hit me up at rory at getfoodio dot com if you're interested.
If you're a random sushi or Chinese place it's worth the 25% to be in the Seamless directory because otherwise no one will ever order from you. Katz's Deli could probably get away with ordering on their own site because their brand is good enough.