Things are worth (no more and no less) what a seller and a buyer agree to as the price as the item. That's the pure, economist explanation, but one that pays little heed to collectors or busy folks who are looking to clear inventory or whatever.
With (for all intents and purposes) a once in a normal lifetime event like selling off a genuine A. Sax saxophone, it's going to be hard to "set a price". Posting here with people may have a better effect, since saxophone "experts" or "collectors" who frequent here may have had this "once in a lifetime" experience more than once. But, even they have seen a "limited field", and their estimates are going to be much more along the guess line rather than ones backed up by real world experience.
That said, there's still no accounting for taste. On any day of the week, you can find fifty excellent Conn horns on eBay, many of which can be purchased for a pittance, and any of which (once restored) will give you an excellent saxophone (within their limits) for a fraction of the cost of a "modern" instrument. Similarly, these "A. Sax" saxes have a value over and above the actual "playing worth". So too might many folks say of the sainted "Mark VI" horns (but not me).
I think that eBay has more than proven that there's a buyer out there for just about anything. It does this by opening up the "awareness" of a particular item, and then allowing people to show you how much they think it's worth.
Having said all of this (and having attended many, many, MANY country estate auctions over the years due to my wife's fascination with them), I have to add that I prefer to go another route when purchasing something that I want and need. With musical instruments, there's a specific protocol that I follow:
1) Do I have enough money to buy it if I can?
2) Do I need it?
3) Do I want it?
4) How much of a chance am I willing to take with the purchase?
I use "Buy It Now" all of the time, simply because if 1) and 2) and 3) are present, I can right then and there decide on 4). But, I never buy anything material (car, house, instrument, what have you) with the idea that the main purpose of the purchase is an "investment".
Well, I should qualify that. If someone is offering up a Selmer Mark VI tenor for pennies on the dollar, I know that it's a no brainer, and (absent any information that would lead me to think that it was stolen) I'll shell out the money.
The difference there is that we all know that the magic "Mark VI" name will drive the price of even the poorest Selmer horn up to a point past the $400.00 that I once bought one for.
So, there are exceptions to every rule. Since there isn't much traffic in wonders like a "A. Sax" saxophone to be found, the answer is going to be a bit hazy.
I see from your signature that you own a couple of "classic" Conns and a Yamaha YBS 62. That's much the same situation as me, so it's obvious that you have an appreciation of the classic horns.
However, there is a big gulf between early Conn and even earlier "antique" saxes. And, I'm not so sure that any manual key saxophone is going to be worth much to anyone other than for a museum piece. There's nothing wrong with them per se, (although manual octave/register keys can take a lot of getting used to), but it's a strong indication that no one's looking at that A. Sax horn with an eye to playing it on a daily basis.
In the realm of collectors, literally anything goes:
We once purchased a very nice (if quite old) house in a gentry-fied neighborhood in a small Illinois county seat. The "rebuilder" had put a lot of trouble into remaking the house into a gem, and it showed at every turn.
Upon moving in, one thing that we were intent on doing as soon as possible was to change the "country cute" draperies for something a lot easier to keep clean and much less cumbersome. (Walking by the gathered bottoms of the drapes in the hall was like trying to move around a very fat woman with a full bell skirt.)
Upon settling in, we started compiling a bunch of stuff for a garage/jumble/tag sale, and these drapes (and their baroque looking rods) were first in line on the list. On top of that, the previous owner had never had them cleaned, so they had "an air" about them.
My wife casually mentioned them at school during her lunch break, and how happy she would be to be shut of the things, as the cleaning bill for them we were quoted ran something like eighty bux.
One of the other teachers asked if they were "Dorothy" drapes, and we (quite frankly) did not know. (This was in "pre-internet" days.) When we did a little digging around and finally looked into the maker, we found that they were. We then were floored by the prices on them in the latest Dorothy Drapes catalog, which also offered such arcania as skirts for lamp shades, skirts for table legs, and so on.
Based upon the catalog, I argued for setting the price at something above the usual "$1.00" sort of garage sale price point. My lovely wife disagreed strongly, claiming that it would scare people off. So, we compromised on something like $40.00 a panel (two to a window), with the thought that we could always go down on the price later. I also got her to allow me to add "Dorothy Drapes" to the newspaper ad.
The ad hit the Thursday paper, and when we came home that evening, there were fifteen (1-5) calls on our answering machine, all wanting to come pick them up early (without even hearing a price first). Everyone who called had a reason why they couldn't wait until Saturday. We ignored them all and waited for the sale to begin.
Also, late that same evening the builder who had customized the old house came by (unannounced) and casually talked about how we liked the house and all, then sprung his question about the drapes and if we'd be interested in selling to him right then and there. When I told him the price, he demurred.
The Saturday of the sale, the people were lining up outside at 5:30 AM, this for a sale start time of 7:00 AM. Once we "opened the gates", the drapes, every last ugly inch of them, sold out within the first ten minutes of the sale. So did all but one of the rods. Ka-ching!
All told, we made about seven hundred dollars that day, with the lion's share of it coming from those disgusting draperies. Yet, had my wife not mentioned them in casual conversation a couple of days before, I would have priced them along the lines of "As is, all for $10.00".
As with drapes, so too with saxophones.
