A 9-year-old saddle is not very old if it was owned by one person and used on one horse. If it were owned by a someone who used it all day every day on multiple horses, it will have more wear to the leathers, but also significantly more wear to the panels (and you should budget for replacement.) I would expect a top price of around $2k for a 10-year-old saddle with a popular configuration in excellent condition, with the price decreasing under that according to demand and condition. The 2002 Butet whose seller wants $2400 belongs to someone who does not seriously want to sell that saddle.
I do think that the older PJ Delgranges have a certain cachet and command a higher price point as they are simply no longer available.
I just finished (I hope) shopping for 2 saddles, so I’ve had my eye on the private sale and tack shop consignment market since March of this year. I’ve seen a fair number of 20-year-old [somethings] for sale and if you look at the panels, they are compressed thin. That’s a sign that the foam has degraded with age. Your horse does not want that and it is a $500-700 repair from the manufacturer for most brands.
Now, if you are budget-conscious and you and your horse are a hard-to-fit combination, this can be a great way to get a good saddle on a budget. I was recently looking for an unusual seat size + flap size combination for me, plus an uncommon panel configuration for the horse, which I knew was going to be a challenge to find used. I went shopping with an eye towards finding that human configuration in an older “scratch and dent” type of model and getting it re-paneled by the manufacturer to suit my horse. If you do this, make sure you know that the panels you want can be applied. For instance, Devoucoux and CWD have both changed their tree design in such a way that they are not able to put their newer style of panel on saddles over a certain age, and if you are thinking “I will go with wool,” make sure you have a saddler who’s said they can do this before buying as not everyone is prepared to change these out.