Bearded dragons are good and the ones at pet shops usually don't cost too awful much. However initial set up will be expensive. Minimum tank size is a 20 gallon for an adult. However I think they are too cramped and prefer a 40 gallon. You will need a heat lamp and heat bulbs. May need another heat lamp with a lower wattage night light for night time if temps fall below 75f during the night. You will need a desert UVB light. The strip lights are generally preferred. The UVB light will need to be replaced every 6 months or so (the UVB output will weaken over time). You need to have thermometers to measure the temperature. Personally I prefer a temperature gun as I can check the temperature anywhere in the cage. None of these things are very cheap so you might be saving up for quite a while before you can afford it all unless your parents are willing to help pay for it.

You have to feed a bearded every day. Babies should eat three times a day. They eat tons of crickets or roaches which will become expensive. My little guy eats 100 crickets a day. The cheapest I can find them is $8.00 for 100 crickets. So, that is $56 each week. Breeding your own feeders is cheaper. However you will also need to feed the feeders.
Once the beardie is around 6 months old they should start being introduced to vegetables and the protein intake will lessen. You can't just go out and buy a bag of salad mix though. Lettuce is bad for them. You should do some research on what veggies they can or can't eat. It can really add up. Nutrition Content has some really good nutritional info.

There are also pellet foods available but many bearded dragons will not eat them. Like most frogs, they are attracted to movement.

Yes bearded dragons are relatively easy to care for if you know what you are doing. However I do not consider them a cheap pet to own. I've spent more money on my bearded dragon than all my frogs and snakes combined.

Personally most reptiles are not cheap to care for (a lot of them have to eat every day). Except for snakes but you don't want snakes. Compared to other reptiles and amphibians I own, snakes are by far the cheapest lol!

I would suggest some sort of gecko, such as a crested or gargoyle gecko. They can be kept at room temperature. They need high humidity which can be achieved by misting. They also need a special gecko diet. Prices vary depending on brand and amount. But it isn't too bad. I can get a pound of repashy for $21.

Sorry for the long winded post. But I didn't want to see someone make the same mistake as me. Everyone told me how easy bearded dragons were and so I did some research and got everything ready. Got my bearded dragon. But then the cost of food really started adding up quick. If I had really thought about how much I would be spending on food, I probably wouldn't have got him. Breeding my own feeders have helped a bit though.