First, let me thank Davide for the wonderful offer to spend summers at his place in Milano. Davide, you are also welcome to come visit myself and my wife in North Carolina. Bring your Alembic, I'll do the BBQ and we'll have a good time!
To Kevin, I too am puzzled as to why a vintage Fender (and I own two of them will hold or increase its value and an Alembic seemingly doesn't. I can only surmise that because Fender has been around so long, is more well known, has the mystique of mojo, etc., is why they're worth more. They're also historical in the sense that at least the pre-CBS models were the first of their kind (Broadcaster, '51 P Bass, '54 Strat, etc.) and as such have a lot of historical provenance. An Alembic doesn't necessarily have that, unless, of course, you get one of the more famous ones (the Godfather, Wolf, John Entwistle's Spyders, etc.) with a celebrity pedigree.
As I noted, I have a '73 Jazz and a '76 Precision. Neither are stock, though if I desired, I could return the Jazz back to stock if I wanted. I've noted that the Jazz basses of that era are going for $3500 or so these days, in good condition. I would consider mine in at least good condtion, and I paid $1350 for it less than 4 years ago, with original (though beat) case. Why are they going up in value? I don't know. Maybe it's because they don't make them like that anymore, they're old, well known? I don't know.
Alembics are and have always been, IMHO, a much more niche instrument than your average mass produced instrument. This automatically limits their appeal to the vast majority of players. Exotic woods, finely machined and produced hardware, extremely close tolerances, unique electronics, etc. do not appeal to most players, for a lot of reasons. Price is one, and for a lot of guys and gals, the determining factor. Their controls sometimes give the average player fits because they're not intrinsically familiar to them (roll off, boost cut active, etc.). Given these and I'm sure many other individual and personal factors, they don't have as wide an appeal as I and most everyone here think they should have.
I think the biggest reason for depreciation, though, is name recognition. I don't know how many times I've gone somewhere with one of my Alembics and no one else knew what brand it was. I don't know why this is - advertising has something to do with it. Low production numbers (compared to a Fender, Gibson, etc.) does too (limiting the number that are out there and other people see). Alembic also doesn't do endorsements, futher decreasing exposure. However, all of these things also permit Alembic, IMHO, to maintain the quality and reputation it enjoys amongst those who know of and use them.
Most folks can't afford a new Alembic. The fact that they don't hold value as well as a vintage Fender etc. is a plus for those of us who want an Alembic but can't afford something new. So I don't necessarily see lack of resale value as a negative in this sense.
As to why Alembic chose to market Flitz as they have, well, I guess you'd have to ask Susan or Mica about that one.
BTW, I bought my P-Bass simply to round out what I have. I always swore I'd never have one, but I do. It is a nice instrument, but a one trick pony IMHO. It has a nice tone, but only one tone for the most part. My Alembics can do it all (well, they can't do a Rick, but nothing else can except another Rick), so for me, they're worth every penny.
My two cents,
Alan