My plot costs just over £8 a year, it has a water trough 10ft away, your allowed chickens and rabbits (though I haven't) the plot is 50 feet by 25 feet ish, not sure how that compare to others?
Although I only had my plot since May last year, I feel I'm in credit. ;D
This year I'm actually going to try and weight my veg and compare it to supermarket prices, just to see how much can be saved. Although I'm not worried about the money, you really cant beat the fresh veg!