Definitely worth selling on Ebay.
I've got a pretty extensive collection myself, and I've known a lot of people with collections of merch as well, and I've never even
seen a copy. I knew they were in Mad, but yeah, copies are few and far between.
Dougs stuff in general can sell from anywhere between $5 (if you're lucky and you find it in a second hand store/stall somewhere, owned by someone who doesn't know their value), to $500 and higher for autographed copies of the more rare stuff ("Trip", the farewell tour songbook, for instance). I don't think you're looking at anything quite that high up the scale, and stuff the Dougs released themselves is usually more valuable, but Mad magazines should sell for enough to make it worth the ebay fees.
Make sure you put the link to the auction up on here, if you decide to sell
