Yes, you're absolutely right. It doesn't make much sense as an investment only, unless it has a special history - "E.C. once looked at this guitar, you know?"
But at least yours has retained its original value, which is rarely the case with most industrially produced instruments.
It would be great to have a crystal ball to see what will happen to the prices of all those signature instruments, or the actual artist-owned ones, in 30 or 40 years. My guess is that the big names like Gilmour, Clapton, Hendrix will gain in value, while a lot of others will fade into oblivion.
