The cost of the lizard should be your last concern. That is usually minor compared to the cost to build proper caging, the increase in your utilities, and the feeding costs involved. Since I'm not as familiar with tegu care, I'll give a quick rundown of a bare minimum savanna monitor setup. 8'×4'×4' bare minimum cage containing around 2' of soil/sand substrate, which usually makes the cage weigh about a ton. Hotspot of 130°-150°f, a diet starting with mixed insects, 100+cricket a day at times, and going to more rodent based as the animal matures. And thats just the bare minimum basic info. Depending on how well insulated the cage isnand the temp of your house, you could easily see an increase of 25 bucks a month or more on your electric. I keep dwarf monitors, and the amount of food they can go through is nuts.