Man customers will complain about anything O_o (sorry just got off work =D)
Seriously OP freeze it. I don't see why this is an issue. If your freezer is so full it can't fit it.. why are you buying MORE food?
It has been scientifically confirmed that if Eiffel was green; he would in fact die.
Do you have a freezer? problem solved
I came up with an answer. Just buy them both and sell the free one to a friend (I'd just gift it since 3 or 4 bucks isn't worth bringing money into a friendship over.)
They do it because they sell more product that way. It's either to push them out or as a loss-leader.
A loss-leader is an item that attracts people to your store specifically for that. It gets the name because you are operating at or close to a loss on the sale of the specific item, but it works because it gets people in the store and they buy other things while they are there.
For pushing it out, it's better to do Buy One Get One Free than 50% off for many things, as people who want two will get two regardless, people who want an odd number might get an odd number, and people who are 'taking advantage of' the deal will will get two rather than none. This works for them because the profit margin on two with one free is the same as the profit margin on 50% off each, so people buying two regardless is neutral, people who buy only one is a gain in that their profit margin is bigger, and people who buy two instead of none is also a gain because a sale is better than no sale.
All that aside, under $4 is a good fucking deal for a take and bake pizza, as the only kind that would "go off" is one that's made with fresh ingredients.
At most of the grocery stores here Buy one get one free actually rings up at half price, so you get one at 50% off.