Generally, when you buy a DVD on the basis that it was cheap, you soon learn that there was a very good reason for that fact. Occasionally though, you find a diamond in the rough.
Now calling Infestation a 'diamond' might be overstating things a bit, but it's at least a semi-precious stone of some kind. A garnet, maybe.
Cooper's a 20-something slacker with a strained relationship with his father and a job he's on the verge of losing due to his complete disregard for the work. It's pretty evident he got forced into taking the job by his dad and is in turn deliberately forcing his boss into firing him.
Said firing is interrupted by a strange, deafening noise. Cooper and his boss both black out, and when Coop finally recovers consciousness, it's to find that at least a day has gone by and that he's wrapped in a cocoon. He manages to struggle free, but almost immediately finds himself hunted by a giant insect: imagine a stag beetle about three feet long and you've got a pretty good idea of it.
Coop somehow prevails against the bug and begins to free his boss and colleagues, but it soon becomes apparent that whatever has happened, it effects a lot more than just their workplace. The city - perhaps the world - has been overrun with giant insects.
Infestation is a comedy-horror with a surprising number of strengths. It sensibly keeps the comedy elements mostly in the dialogue and human interactions, rather than playing the monsters for laughs (it does break this pattern at one point, alas). It also skips the usual tortured explanations of where the monsters came from, which is a smart call from a pacing perspective. Plus it boasts a surprisingly strong cast and decent physical effects (the CGI, on the other hand, is rather weak at times).
If 'giant bug movie' is not an instant turn-off for you, Infestation is worth a look.