I have a 4" DPA5906, a 5" DPA5906, and a 5" DPA5903.
I feel the 4" was worth the 2x price I paid for it. Trigger pull isn't that much lighter than the standard 5906, but a lot smoother. Haven't shot it enough yet to really gauge accuracy, but it appears to be very accurate and I've never seen a PC gun that won't easily out shoot a standard gun.
The 5" 5903 has a trigger pull very similar to the 4", maybe very slightly lighter pull weight. I haven't shot it much either, but it appears to be every bit the tack driver as the 5" 5906 and I like the balance of it better. That being said, I just use it as a backup gun to the 5906 since I feel the heavier weight should help with follow up shots. FWIW, I paid about $900 for it.
So as for the 5" 5906, the day I no longer own it is the day I die or am homeless and hungry!
I probably paid 4x current standard 5906 price but I'd go so far to say its worth 8x. It will hang with any $3K 1911 that I've shot enough to evaluate (a Nighthawk, 3 or 4 Les Baer, and a single stack STI something or other). I forgotten what the spec is for the PPC 5906 but I remember checking a this gun shots it with UMC 147gr off a rest. It has a noticeably lighter trigger than my other 2 DPA's and is even smoother, so I suspect the former owner has changed mainsprings. I need to look one of these days but it has ran flawless for probably 5K rounds and I didn't get the other two until recently for comparison. I shoot it for USPSA and 3-Gun using the old model 59 20-round mags and have been extremely pleased.
So if you can benefit from the better accuracy and better trigger then I have found them to be well worth the money. I don't think a finer gun can be had $ for $. As for the price on that gun, that is probably a little high unless it was NIB. $750 to $900 is more the going price for the 4". If you want a 5" that is a different story. I've only seen seen three 5906's and two 5903's come up for sale in the last 3 or 4 years. They are worth the price at which you or the guy(s )you are bidding against chicken out.
My $2.