We’re talking about two completely different scenarios.
You’re staying on the P1 upgrade merry-go-round - of course there are good inducements to keep you on the ride - there have to be - even in your case of a ‘cross-grade’ (which was never initially supported when the 2xx series was released).
I’m talking about cashing-in and getting out (or buying a DB out-with the P1 ecosystem) - completely and utterly different in every way imaginable. The IQ1 series is 5 years old. In 5 years time, take your 380 to your local P1 dealer and tell them you want to sell it, or trade it in for - say - Canon gear. Then get back to me with their offer.
Jim
P.S. Since you can get $22k for an IQ180, maybe I'll send you a few that I can pick up in the low teens - you sell them, and we'll split the difference (less expenses). 
No - we were talking about the exact same thing. Your words:
Look at an IQ180 as a final example. A P1 dealer (who you are on good terms with) - might - on a good day - offer ~$10k trade-in.
But sure - feel free to move on from that and change the goal-posts. Now you specifically want to discuss trading in against other gear, or trying to sell through, or to, the dealer.
Well guess what - it's not the dealer who's funding that 22K trade-in value.
And frankly, you'd need your head examined if you wanted to get the best price for anything by selling it to someone who makes their living by adding a margin before they then sell it on to another private individual.
And if you read my post carefully, rather than reading what you wanted in it, and twisting it to suit your own ever-changing argument, you'd actually hopefully have a little more intelligence than to accuse me of "staying on the P1 upgrade merry-go-round".
I bought my back second hand from a private individual. I'm playing the system to my own advantage because I have never - and would never - personally buy a brand new back from a dealer. That's where the big margin is - in the cash sale of a new back.
$27.5K approximately 4 years ago for a back that, IIRC, was around 15 months old at the time, and had the remainder of a 1 year additional warranty to run on it.
4 years later. Another outlay of $15K to get a brand new back that comes with a 5 year warranty.
Come back to you in 5 years time with an update? I've got better things to do with my life.
But just to entertain you, let's say that I did want to get off the "merry-go-round".
Option 1 - trade in to the IQ3 80, and then sell that on immediately.
What price those on the second hand market do you reckon?
Well, it would appear that the list price of the thing is $44K -
https://www.digitalback.com/product/phase-one-iq3-80mp/What do you reckon I could shift one for to a private individual? Brand new. Boxed. Untouched. 5 year warranty. Do I hear $30k? Seems reasonable to me (after all, I was happy to pay 27.5K for a 15 month old IQ180 a few years back that had 9 months warranty left on it).
Total outlay, $42.5K ($27.5K that I paid for the 180, plus $15K trade-in cash for the 3 80)
Cost to me to own the IQ180 for roughly 4 years - $12.5K. $8.50 a day.
Option 2 -
What if I do just dump the thing and sell it to a private individual for, say, $12K.
Cost to me to own the IQ180 for roughly 4 years - $15.5K. $10.60 a day.
You think that's a problem? Seriously? Ten bucks a day?
That's what people make (before tax) flipping burgers in McDonald's in one
hour.
Just one single image sale has paid for that entire ownership period. Am I'm not even a professional.
I think you're punching above your weight if you think the cost and depreciation on these things is a problem.
