There is a 2.5" Python in the classifieds that I really want to pull the trigger on but haven't. I notice that it is still listed which appears ot lead credence to my theory. Bullets for anything other than a 9mm are prohibitively expensive for one who does not reload. I like to shoot 158 gr JSP in a .357 and the best price I could find for a thousand was around $550. This as opposed to 9mm at a price of $220 delivered. I've already got two 357's that I don't shoot due to price of ammo and I can't see adding a third even if it is a Python Snubby or that 3.5" 27 that Pangris has listed.
Sad reality.
The new Colt Pythons were selling hundreds above MSRP for years and venders could not keep them in stock until recently. They're still popular and selling well as are S&W, Ruger, and Taurus revolvers. You have to be careful about taking anecdotals and correlations and then making broad assumptions and seeing causations that aren't really valid in the grand scheme.... Ammo is expensive, but people can still afford it. People are still shooting and can afford to buy 223/556, 7.62x39, 308win, 45acp, 10mm, etc ammo and the guns chambered in these calibers. Guns chambered in those calibers are still selling well. What makes you think that people can't afford to shoot 38/357 anymore?
That Python could still be listed for a plothera of reasons, but you seemed to paint a narrative behind one possibility which is ammo prices. It could be the price of the Python which and most do not want to spend that much money. It could be that the Python is used and the OP is claiming it's new. It could be that most don't want a Python with a 2.5" barrel, and it would have sold a long time ago if it had a 4" barrel. It could be that it's just posted on the wrong forum, and it would have sold quickly on the Colt forum or GunBroker....
There are a plothera of reasons why that one ad didn't sell. If your narrative is that the Python still hasn't sold because revolvers have fallen out of favor because of ammo prices, then logically other revolvers for sell in the Marketplace shouldn't be selling either right? That's not the case, and that alone disproves your theory.
My theory is it's because the 2.5" Python can be had REALY NIB from a FFL for under $1300, but the
seller is selling his used Python for $1400. Next, I don't believe the 2.5" are as popular as other barrel lengths. If the OP lowered his price to $1150, I'd bet it would sell quickly.