The only disadvantage to acrylic tanks is they can scratch. Other than that, they have the same general disadvantages and advantages as glass tanks (except for weight, as acrylic is lighter...but thats the only real difference between glass and acrylic tanks).
Like glass tanks, acrylic tanks can be expensive (maybe more so than glass as you can find glass tanks real cheap used, not so much the acrylic).
As for prices, I have not really priced acrylic tanks, as I find they are no better for me, than glass tanks (other than lighter weight). They are about the same or more in cost than glass tanks. For companies that make them, a search on the 'Breeders/Dealers/Stores link above under cages, will show many places that make/sell cages, though not all will use acrylic. The kingsnake classfieds will have some listed under the 'cages' section and doing a google search on 'acrylic tanks or cages' will bring up alot of hits as well. Then you can compare prices, shipping costs etc.
The cheapest way to go for dragon cages is to build your own. Even if you lack any carpentry skills, there are plenty of ways to get somebody to build it for you. Many places online will sell cage plans/designs for a pretty cheap price. Many regulars here will be happy to send you plans for free, just need to ask. Or you can just describe what you want to a friend/family member, bored retiree, student (who may love to do a project in woodworking glass, or a teacher may love to have such a project to give his glass to work on), etc.
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PHLdyPayne