Dentistry, and specifically the branches of dentistry that deal with dental prostheses is full of little gadgets and knick knacks that seem to have a very large overlapping areas, the same thing is done with a slightly different name and gets to be treated (and priced) like a whole different prosthesis altogether. A great example of this is the partial denture versus bridge debate. At what point is a partial denture a bridge? Why is a bridge so much more expensive than a partial denture?
The issue is one of functionality but also one of semantics. While certain things can definitely be classified as a denture, it is harder to see what the difference between a fixed partial denture and a bridge is. Bridges cannot be removed, and are always fixed. If you can take it out, it is an removable partial denture although you may hear people talking about removable bridges, but that is just marketing. Bridges are fixed to teeth and work as bridges, they bridge gaps in your teeth, and are fixed to a tooth or to a dental implant. Also, bridges only bridge gaps, they cannot be thought of as replacing all of the teeth in a given arch, that is a full denture.
So if the difference is almost always semantic, what is the difference in price all about? Well, making something that is nonremovable will always be more expensive than something that is removable. The materials also determine the price. If you have a denture that is full acrylic with a nice resin plate than it may cost more than a fixed bridge of average quality, for example, but on the whole, removable dentures are usually the cheapest solution, while bridges tend to take more work and precision and need to be made of better materials, and as such will usually cost more money.