Heh, I assumed you wanted a low cost solution since you were asking about the cost. The camera I mentioned is indeed a low cost solution, cheapest I know of. Range isn't very good, I haven't been able to go past two walls indoors. Image quality also suffers (at some point when camera battery was running low, I got only b/w images).
If you would like something of higher quality, a CMOS camera would be much better suited. Of course, there's still the problem of transmitting and encoding that data.