It can be done, but numbers make all the difference, well that and reigning the wife in. We had ours at a beachside restaurant i a VERY expensive part of country and came in under 3 grand including free booze all day and food.
The venue was reasonably cheap, but we saved by only having about 30 guests to the day bit/food and having a 'posh' bbq put on by the restaurant. No photographer (what a rip off they are), wifes friend made cakes for nothing, i-pod hooked up to stereo for music, my vintage suit from ebay, her dress from highstreet (not wedding dress), no flowers. My old boy paid for the booze all day for everyone, which is pretty much all anyone can remember from the day and went down a treat.
Only extravagances were her hair, '56 Buick to get us there, and £3 for the sandbanks ferry to get us to the reception.