If you're in to building stuff and have tools. I'm pretty sure a cage could be built for well under 100 dollars. 200-250 is what the average first time builder spends. If you look on craigslist for building materials, you could probably get a 4x2x2 built, slate bottom, DIY fake rocks for ~50 bucks.
Stuff's expensive, but it doesn't HAVE to be as expensive as most people are saying.. I don't know how you spend 20 dollars on greens. My dragon could have the most varied diet in the world and there's no way in hell he'd eat even 5 bucks in veggies a week. I spend around 6 or 7 and throw away more than half when they start looking bad. Not to mention, there will only be a very short time where he is eating a LOT of veggies AND a LOT of crickets if he does at all.. They start off eating mostly crickets and move to eating mostly veggies.
Vets can be expensive, but I just got a fecal/exam/prescription for pinworms for under 75 dollars.
My lights and heat cost around $2.50/month
60 a month for freeding one BD? You're already on the internet, you really need to use it to order your bugs, or start a colony...
So ya, it gets expensive, but paying 600 for a BD setup is kinda like paying sticker at the car dealership. If you really research and hunt down some deals you can get a Beardie and a complete set up in the 150 neighborhood, and running costs around 20-30 bucks a month.
General upkeep on two dragons probably costs me $800 a year. That's lighting maintenance, power, and food. If you throw in a medical emergency, then those costs shoot up tremendously. I spend more on food then I need to, but allergies keep me from raising my own colonies. No matter how you slice it, reptiles aren't cheap. Which is probably why the first year mortality for pet reptiles is something like 85%...people buy the $40 reptile and aren't prepared for the upkeep costs.
When my female dragon was young, I raised her on Phoenix worms. She could eat $5 worth in a sitting...factor in multiple feedings a day, and she cost more to feed then I did!