I agree slabbing ASEs a waste of money (other then 1 for my type set all i own are raw) As a matter of fact, unless you are specificaly collecting the whole ASE set or like me a single for a type set, I can see no reason to have them graded. On the other hand it is a gift from "Mom" and probably better that she gets them slabbed rather then getting stuck with fakes
Mom knows you like coins. Especially ASEs. She knows an easy and convenient way to purchase 'em. Doesn't have to drive all over town to buy them. Mom loves you......graciously accept the gifts and don't say a word.
There's your question and answer right there. If you received a gift from someone for whatever reason, I highly doubt you'd be so crass as to ask how much they paid for it, be it a necktie or a set of golf clubs. Your mom spent time thinking about your gift, researching it (to whatever degree she did), making the purchase knowing this was something dear to you, and ultimately giving it to you with the hope that you'd treasure it. Honor her unspoken request to do just that. Treasure it and maybe you'll ultimately pass it down to one of your kids or grandkids from their grandma or great grandma. You've got a very special mom who cares not only about you but about your interests too. You're a lucky guy.
A parents love is priceless, a child's most cherished gift to parents is to return the priceless gift with no price tag!