We could also approach this with a cost/benefit ratio. We can assume that a guitar will cost a certain amount of money, just as stocks do. We can assume that just because two guitars or stocks cost the same amount of money, they may actually be of dramatically different quality. We may also assume that there are situations where one type of guitar or stock is worthwhile to one person and worthless to another, with the opposite true of other guitars or stocks.
Moreover, we could assume that some guitars and stocks are priced at very low levels due to nothing more than market perception, and that these are real steals for people who are willing to put in the time and energy to do their research. Likewise, there are guitars and stocks that are priced at ridiculous levels due to market perceptions, and these can really burn people who expect a lot more from their investment. And, we can also assume that just because a bunch of guitars are the same model, or a bunch of stocks are in the same category or business, that doesn't mean that they play equally well or sound equally good, that is, their returns will vary.
A major disservice may be done by saying that "All guitars of brand and model "x" are really great", just as doing the same with stocks is a poor idea.
We may love Guilds, and have excellent Guild guitars, but that certainly does not mean that they are all good. There are bound to be a few clunkers out there, perhaps many. There might be 20, 30, 40% crummy Guild guitars out there. (A recent article about TJ Thompson had him stating that 40% of Martin OM18s were not that great.) There are crappy MArtin D45s, crappy Gibson J200s (lots and lots of crappy J200s), and crappy Guilds.
The upshot of this long winded wall of words is that one must decide why they are buying a guitar, and then diligently search for that guitar. Looking for a bottleneck blues guitar? You probably don't want a Guild D40. Looking for a bluegrass guitar? Stay away from a Harmony Sovereign.
The hardest thing to realize in all this is the limits of guitars. There are guitars that are just lovely, wonderful instruments, but which cannot be used to perform certain kinds of music by certain kinds of people, no matter how hard they try. Diligence is the key to finding a guitar with the right sound, right neck, right frets, right action, right balance of strings, etc. It's too easy to buy some flashy expensive model and be disappointed, just like buying the most popular new stock is a way to simply lose money. (Facebook, anybody?)
My best guitar buy? A Hohner D1 Gruhn design, for $45. A wonderful, solid top guitar with a fantastic sound, nice size, and great neck. Its major issue was that it had the name "Hohner" on the headstock. If it had said "Gibson", it would have commanded $1,500 in a heartbeat. I have played the heck out of the guitar for 12 years, and it has always responded. I've expanded to other guitars, but the Hohner is still a killer.