Defunct Company Gear Value

For the most part Larryi is correct, the prices will initally drop dramatically. As J.D. points out with Dunlavy though, some will hold their value remarkably well.
Threshold is another example of a company that went out of business that's products hold remarkable value, even the Forte line.

Threshold and Dunlavy are not the norm though.

Interesting thoughts given that a lot of very nice sounding gear is designed and manufactured by what are essentially one-man operations - think Vladimir Lamm, Judd Barber, Ken Stevens, Jim White, Ralph Karsten, Kevin Halverson, Steve McCormack, Keith Herron, Emmanuel Go, Wilson Shen, Steve Nugent, Mike Sanders, Joseph Chow, David Belles, and many others. We are fortunate these guys have had passion enough for what they do to share their work with us for many years.

To the question, most tubed gear should be repairable and much of the better solid state gear will last a long time without needing repair. Of the SS gear that fails, I suspect much of it can be repaired by replacing available parts when serviced by a specialized technician. There are guys out there that know this stuff well enough to fix it, but probably not as well as the guys who designed and built it with regards to the sonic trade-offs of using different parts.

Jmcgrogan, When Threshold went out of business prices immediately dropped to thirty cents on the dollar. Prices did not improve for used Threshold until Pass Labs became popular. Even though some used prices have improved for used Threshold equipment a quick look at the blue book indicates Threshold prices are still low for most models with some as low as only 25% of original value.

Rgrog, I did say that prices drop dramatically initailly, for any company that goes out of business. However, some do recover. There is a pair of Threshold SA-1 monoblocks on Audiogon now for $4750, that comes to 79% of their original $6000 list price. I think that's holding value pretty well for a pair of 25 year old monoblocks.
I know not all Threshold's still sell for 79% of list, but they seem to do very well on the used market compared to other defunct companies. They even have their own website, Thresholdlovers.com, not many can say that either.

FWIW, you can get good deals this way. I'm currently enjoying a pair of Soliloquy 6.3i's that I paid less than 22% of list for. I thought they were a very good value at their original price, even better at 78% discount.

Jmcgrogan, I noticed nobody is dying to buy the SA-1s at $4750. Asking price is one thing, actual selling price is another. I have been following prices on many items for a couple of decades now and every once in a while a piece of stereo equipment will show up at a ridiculously high price. I know there are some variables in equipment pricing like cosmetics and how the equipment has been maintained, however, based on this site's blue book SA-1s sold new for $8,500 with a used price of $3,170.