J.V.
I'd say $20 or less...unless it's a super close friend and then you might consider more.
I think babies would enjoy receiving a little board book. They have really cute ones at Barnes & Noble and borders...Dr. Seuss(?) for $4.99...You can buy 4 of them and then be done!
As my daughter grew older, I would buy one chapter book and then insert money equaling the child's birthday number.
Just a hint, I buy things when they are on clearance and keep them in a box under my bed. When it's birthday time, my daughter "shops" from that box and then we aren't stressed trying to find a gift at a good price. I even do this for some adult gifts. I buy clearance Bath and Body Works stuff for little teacher gift bags. If you keep a kid under bed box and an adult one, then you have lots of nice gift ideas for cheap!!
J. K-V
www.AisForAutism.net