I've been thinking of getting a trail cam mainly for use in the garden, particularly at night. Have you ever had one?
I've looked at a few (on ebay) and it seems you can get a reasonably decent one for under £60
I haven`t mate and don`t know anything about them.
If they`re anything like camera gear, I should imagine people buy them as a fad and then lose interest / upgrade and sell the old ones off cheap.