Like you I have plough in my hard cash for theses call swiss mechanical. Like you I also weep on the moment my friend told me how low they pay for the same watch that I have(Seamaster James Bond) thru used market. They always tease me on I should wait till it's available on the used market.
I did what they said, only to see the price of the watch tripled (PAM 249) and lose the chance to buy it.
Am I upset? You bet.
But that's life.
Through out all these years I have learn a few things.
1. The collectable market is just like the share market. For 1 gold nugget there's many lemons.
i.e. For 1 PP5970 there's many quartz Twenty4.
2. The seller will never tell you which is the nugget but gladly sell you all the lemons.
i.e. Ever try to ask for PP5970 or better yet the SS Daytona black dial at retail price? Forget about discount.
Consider yourself lucky if the price is less than 15% premium.
3. This is the best I have

The nugget always appears to be less desirable than the lemons.
i.e. A 50s/60s Omega Constellations Pie Pan dial could be had for RM800 or less and you can go on and buy lots of them because no ones like them. Great movement (better than rolex!), Super fine dial and in gold some more. All stop until 3 years ago. The price now is about RM3k~RM4k.
Here is where I tell you that I'm not that smart. I didn't get them at ratus. Ribu is what I paid. Why? because 4~5 years ago everyone is into big watch. No one care for these little jewel (34mm~35mm). I sure didn't and when I did it was too late. Price have gone up.

This sort of info is not easily obtainable and have to spend time going deep into research and understand how the watch industry works. Then maybe we can land ourself a heavily discount unpopular watch but price will grow 4~5 times over the next decades.
There are people doing this for living and they are sharp, fast and financially equip. Not a easy game to win, my friend.
It sound to me you're frustrated about your watches losing value. May I ask does that makes you love them less?
That's the ultimate goal isn't it? We are into this because we love watches.
Regards
T