Hi Again!
I am always wary when lots of a particular instrument are available secondhand - why? I have a BW curved Soprano Sax. The only decent step up would be a Yanagisawa which is nearly £2000, and the BW has a very high rating. They are both very good - just try and find a used one. Plenty of Yamaha Trumpets, Cornets and Trombones available secondhand also. I do not have THE answer, but my speculation would be that either too many are bought and people move on to "Better" instruments sooner rather than later; or that people religiously follow the path of beginner - intermediate - professional instrument without necessarily questioning it (with Yamaha saxes its 275 - 475 - 62 - 875). Try and find a used BW sax, and you will realise that people tend to hang on to them, rather than trade them in - monetary value is fairly irrelevant if you don't sell it. Also price is influenced by supply so I would be surprised if you would lose much if you ever did decide to sell a BW, for example.
Pete Thomas reviewed 4 Tenor Saxes recently (2 Vintage, a YanagisawaT901 and a BW - generally rating the BW highest!). £500 should get you a decent sax, used or otherwise, and you may be very happy with a YAS 275 at that price - the BW usually comes with a Yamaha mouthpiece, and the two recommended above are both very good.
Kind regards
Tom
😎
Sax Heaven in Oxford has quite a selection of Alto saxes from £239 - £495, including BW, used, and Vintage so you could try some of them out for yourself if you can travel the 32 miles from Stratford. They also have a YAS275, which you could try by comparison (costs £849). I have no allegiance to either of the companies that I have mentioned, but I am concerned in value for money, and that certain brands can dominate the field without necessarily continuing to justify such reputations/price.
Final Addition: have a look at
www.shwoodwind.co.uk where there are several reviews of Alto saxes amongst others which may help.