I have seen those as well and they are not that expensive. About $89 to $159 is what i have seen thus far.

The ones I am looking at are wireless webcams ( up to 10 frames per sec ) and you can get those for as little as $69 to $129, or as little as $19 per cam for wire variety.

---------------------------------
1/10 - 1/4 acre pond plus 16 ft deep/ Plus 40 ft by 20 ft by 6 ft deep koi and fathead minnow pond next to it. Upstate NY