Well as for the dog/cat example you can just buy a big bag of food an your set for a couple of weeks... As for feeding some people dont have cheap sources/good sources ( I know a guy who spends 200$ every 2 weeks on his monitors and he has 3 but his bill could go down 150$$) ( thiers also other people who spend as low as 7$ on a sav a week, and others who spend up to 20$$ for a sav a week all depends on your food source)
I never owned a tegu (or plan on owning) so I cant say anything about them... Also baby monitors ( and adults ) need a veriety of differnt foods .. babys need crickets,worms ( I feed super worms) and mice ( roaches work well ),.. as for adults they need a diet of some birds as well as rats. So people feed quail,chicks,and mice and some people even use thoes big hissers and other big roahes too feed their big monitors... As for cageing a 8X4X5 cage is pretty big not all people have that much space for their animals and others have alot of room! I really dont know your personal situation but just saying anyway....
Just trying to help....