Get her a handful of dirt. Geez. Don't think of the cost of a gift think of how special it can be. A trip to Bermuda is nice but a hug and a kiss and letting your mother know what you mean to her is not only cheaper, but it means a lot more.
The best cheap thing that doesnt cost one cent thats priceless but is worth million is a big hug a huge kiss and tell her how much you love her and how much she ment to you and tell her you will love her.no matter what ;)