i think guitar stuff dont appreciate mainly because it is technology related... technology tends to improve, thus phasing out the old ones (in effect, makes them a lot cheaper).
the only way for guitars to appreciate in value is when the world runs out of wood... then your lumanog that you got for 500 php would suddenly be worth 3K. that wouldnt happen anytime soon though ...
another way is to be endorsed for free by a new guitar god. though i doubt the world will have a new guitar god soon that will turn a made in japan aria pro into a collector's item. the last guitar hero (im using the term loosely) who came out was Tom Morello, and i dont think he made any guitar more expensive than it should be (he is a fan of cheap guitars btw). the new guys are good, but i dont think they have achieve the stuff that made yngwie, paul gilbert, van halen, etc. guitar gods.
i have a washburn dimebag darrell ... dime is dead and i think washburn discontinued their dime signature guitar line (dean hold's dime's name) ... im not even sure whether this guitar has increased in value, if it did, i would gladly trade this for the dean razorback. i think the new one has better specs...
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for stomp boxes to appreciate in value, they have to be made in small quantities, but with a great demand, then suddenly, they get discontinued... now that's a sure bet to make those "cheap" stomp boxes appreciate in value. another way is to have a famous artist associate his sound with an unknown, cheap, discontinued stomp box, that will certainly increase the value of that particular unknown stomp box.
fat chance for boss pedals to appeciate. i wonder though, have you guys ever tried a discontinued boss pedal that sounded so good? i havent... i just tried out a boss CE3 chorus awhile ago, its made in japan and it has that mode where you choose between stereo and mono chorus. i dont like it. i think it deserved to be discontinued.
i also played DOD pedals ... and nothing really interested me or made me want to hunt down a rare discontinued DOD pedal. i love the DOD grunge and Death Metal pedals, and well, thanks to digitech, they are still around... so im not afraid that they will run out soon.
boston... now, if they get sued and discontinued, i think their value would appreciate a little... not that much to rival boss products, but maybe 20-30% appreciation perhaps.