I paid $3500 for my 1994 E350 six years ago.
Body / Frame in good shape. I thought it was a little high, but I had my heart set on that year and body design. Cargo van, windows in back, and in the side cargo area door, no turbo, and very minimal denting. I am not into performance. I want reliability and durability. And minimal electronics ( it's E4OD requires a computer module ).
Which US Shift makes a generic replacement for.
I did not want to tease the obsolescence monkey where unobtainable parts risk my investment.
Minimal rust. Southern California but 30 miles from coast. Had transmission issues of an electrical nature ( was an intermittent PSOM in the signal circuit. Frustratingly, gauge was steady ).
A lot of delayed maintenance needed to be done. I put another $20k into it ( entire HVAC / engine cooling system, all fluids , hoses, and filters, tires, rear differential, brakes , front suspension replace, including steering box, troubleshot transmission problem, eBay PSOM, new glow plugs, rewired to manual control w/White-Rodgers contactor, electric Carter fuel pump, new alternator, new starter, new batteries ) before I trusted it enough to do DD service.
It was a rescue from a landlord PO that had gotten it from a renter in lieu of rent, and had used it for several years as a storage locker.
It still needs upholstery work and a fresh coat of paint wouldn't hurt, being a white van, I just rattle canned it with Ford white touchup paint to prevent rust.
So, I'm now into about 25K$ for something that's mechanically sound but still looks like an old van. I have not done any injector work yet. I don't usually fix stuff that ain't broke yet, unless it's obviously worn and presents a safety or reliability risk.
So, I say you are in the ballpark.
Something that is too dilapidated to fix... Part it out.
If the body and frame are decent but it has a lot of deferred maintenance, like what I had to do, low end sale price. Someone's gonna pay for a lot of parts and invest a lot of time.
If its well maintained, but just a reliable old utility machine. I'd guess around 10-20k or so, depending on area and cosmetics.
Now, if you've got everything all gussied up...thing looks like new...got expensive toys in it, then someone else may give you top dollar. I wouldn't, because the fancy stuff is overkill for me and I would not pay extra for bling. I would think blinging one out would be risky investment, as that's too much into some particular individual's taste.
I do not know if others value an IDI enough to compensate for it being older. I valued it for it's repairability and it's older design. I grew up around older technology and hate new technologies protected with computers that enforce business models with a purple passion, I hate LCD displays during the day, and I hate controls I can't operate by feel. I wanted something I could modify if I want. Like using choke cables to control the HVAC vents because the old vacuum operated actuators we're sticking.
I place a lot of value in the peace of mind knowing I can keep my stuff working, even if it is old, because it was designed to be disassembled if needed.
Hence, an IDI is more valuable to me than the later versions which have more complex and expensive innards.
My biggest fear is my own government will take it from me by refusing registration renewals..
Price...it's a tradeoff. And you aren't pressured to sell, so no sense to give it away. You can choose your buyer and you know what you have. Pick a good buyer who knows what these are. An ignorant buyer will just cause all sorts of grief.
You strike me much like the PO of my van. Just an honest guy trying to re-home an old van that still ran but sorely needed work done. I wouldn't say I got a helluva deal, but looking back, I feel I paid a fair price for it, six years ago. I've put a helluva work in this thing and got most of it just right by now, and for all purposes, it's now family.
To price it now, I'd guess around 25-30K, but I would have to wait for the right buyer. They aren't making these anymore.