I have never been to a store that offered a "Buy X get 1 free" deal and the one free was not the lowest priced item. If it was customer's choice, it would be a bunch of jackasses buying five $2 cigars and picking out the Opus for free. The store has to protect against those types of people and that seems to be the only logical way to do it.
If you are going to go in and buy 15 cigars and get 3 free, why not go in Monday and buy the five most expensive cigars and get the sixth most expensive free, then do it again Tuesday with the next 6 and Wednesday to get the least expensive. That way, you'll get one high dollar, one medium priced, and one cheap cigar free, instead of 3 cheapos. Plus, you'll get a lot of face time in the shop and they may be more likely to let you know when a box of rarities comes in.