i doubt it. chances are they will only go up in price as they become more advanced. have more advanced cellphones become cheaper over the years? have powerful computers become cheaper? no. chances are, 3D Printers are not going to become cheaper.
buying one is a bad idea. they have them at some stores and will let you use them for a small price.
But technologies of equal advancement separated by a decade will experience a major price gap. Sure, in 10 years, a 3D printer that can print at the nano scale will be expensive. But, a 3D printer that prints simple plastic then will cost about as much as a paper printer costs now.
When anyone refers to technology becoming cheaper the longer it is used in mainstream refers to this. How much does a flat screen monitor cost now? Cheap as compared to when it first came out. How much does hydrogen technology cost now? Expensive as forget, but will get lots cheaper as we integrate it into society. Technology gets expensive because of the intricacy of the newer systems. An iphone is much more involved than a flip phone, comparing their list price, accounting for inflation, and all that jazz, so of course it will be more expensive.
Printers are difficult to talk about with prices, though, because companies always cut the price for the printer itself by up to 90%, and get the profit from the cartridges. The format that 3D printer "cartridges" take in the future determines the price of the printer. If we use the current system, where only wires of plastic are used, then it can be expected that 3D printers will be expensive, because the companies won't get much back from the plastic. This is a better system, though, because that means it would be cheaper for the consumer in the longterm.