I don't think they are "moronic" to ask what your bottom dollar price is...you must have given it some thought when you listed your item...correct? The "OBO" listing is optional to you...it gives the buyer the impression that "you will take less", he/she simply wants to know what it will take $$$ to close a deal "NOW"...quick and simple.
Auction is for those that like to dicker...I never go there.
On the other hand, "OBO" does imply "or best offer", ie...you expect them to make an offer so I understand your point....to a point :D
Dave