The place that I get my frozen rodents from charges what amounts to $1.75 (shipping included) per mouse for a 25 pack. A little cheaper than the pet store. Of course the more you order, the better deal you get.
Now for the down side - will your snake even take f/t? Also if you are only feeding one snake you're looking at the possiblity of the mice getting freezer burn or getting a little funky after about a month or so after you cut open the package. I usually repack them in freezer storage bags after I open them, but they still tend not to be so fresh the following weeks. I have some snakes that won't take them after a certain time - and some don't really care you could feed them rancid roadkill (LOL).
As far as space goes - I here is a picture of a 25 pack of rat pups - mice would be the same size.
Hope this helps.

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Tosha 
"One of these days i am going to wake up..look around...and realize my place looks more like "Ace Venturas"s than my own." Coldthumb
7.33.0 Ball Python (Harry and Fluffy and gang)
1.0.0 Angolan Python (Skywalker)
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