The problem with ready made frames is twofold:
1) Most movie posters aren't a perfect 27x40" and
2) Posters are spray mounted to matboard before they are framed (unless you want unwanted rifts and waves).
Solution?
a) Spend $80-100 for custom framing like I did or
b) spray (dry) mount them yourself which I also do. I prefer using foamcore to mount posters.
Supplies: spray adhesive (e.g. 3M Super Spray 77, 16.5 oz.), a brayer or roller, straight edge, x-acto knife, foamcore.
DIRECTIONS:
1) unroll poster onto newspaper so that back side is facing up
2) Spray conservative amounts of adhesive onto poster.
3) Transfer poster to foamcore and **carefully** place bottom of poster on bottom of foamcore (you may wanna ask someone to help)
4) Take brayer a slowly roll the poster onto the foamcore using short up and down motions

5) Finish rolling the poster corner to corner, let dry for a few minutes
6) Place straight edge on the inside of the poster and use a sharp blade to cut. Cut in one direction (toward you). Make sure you don't dig real deep on the first cut. Instead, make 5-10 careful cuts until the excess piece comes of naturally.
7) admire your work of art!
NOTE:
You may have to cut off some of your poster if it's too long. e.g. you may have bought 30x40" foamcore and your poster is 40.25" long. Cut off excess poster AFTER mounting it. I've seen 40x60" foamcore thus making this a non-issue.
COST of supplies:
$40 for brayer, glue, and knife...straight-edge extra
$5 per sheet of foamcore (unless bought in bulk)
Cost to mount 1 poster: $45
Cost to mount 2 posters: $25
Cost to mount 5 posters: $13
Cost to mount 10 posters: $9
I think just a simple spray mount looks better than the standard 1" metal frame...no glare, smooth looks, lotsa compliments. 3/16" foamcore is typical, but dickblick also sells ½" foamcore. The only down side is that long-term protection from the elements is non-existent.