For insurance purposes, you're probably going to want to get to a typewriter shop with an experienced tech. Take them your list and all the photos you have, then have them come up with fair values for working machines.

Maybe give Paul Lundy at Bremerton Office Machine Company a call and see if he can help you out. https://typespec.com/remington-model-9-from-1937-is-a-beauty/

He may not be local to you, but he may be able to give you good data for insurance purposes.

Typewriter pricing is fully determined by the seller regardless of the model and condition. It's possible to find a fully functional model in pristine condition being sold by one person for $50, and the same model in rough shape and requiring repair from someone else for $400 - in the same antique market.

I would take your list of eight typewriters, find examples that are in good cosmetic and working condition on eBay, and use those prices - including shipping - as proof of what they are worth. Conversely, post your list of machines here and we can weigh in on their availability and perhaps provide a rough average for replacement cost.

Uwe wrote:

.... snip .... pricing is fully determined by the seller .... snip ,,,,

Uwe, I have to respectfully disagree with your assertion that pricing is fully determined by the seller; I contend that the price of any item or commodity is, in the absence of trickery (including deception) or force, always determined by the buyer.  The principle here is that there is no price, i.e., no sale, until a buyer voluntarily gives the agreed value to the seller. A seller can ask whatever, all year long, but there is no price, i.e., no established value, until a sale takes place.

Now, there might be some unspoken nuance in your post, like in the antique marketplace example perhaps you were equating "price" with "asking price" and by "being sold" you mean "being offered". And with the eBay example, you expect readers to know to look in the "Sold" listings rather than the unfinished auctions listings to see actual selling prices.

In your marketplace example, it is possible that those two typewriters actually did change hands, were sold, at those prices, but I argue that it was the buyers' agreement that set, established, the prices, not the sellers' hope.

(I also suggest a corollary to this principle: In the absence of trickery or force, you cannot cheat a seller. A seller has all the time in the world to research an item and discover its potential value before offering it. If s/he does not do that, s/he cannot claim being taken advantage of by a more knowledgeable buyer.)

That corollary regarding sellers is based on research and also applies to buyers but in a less strict way. That is, it is possible to cheat a buyer and this is because of the limited time a buyer has to learn the value of an item s/he simply stumbles upon. A seller can disguise a known defect or keep up a distracting patter to prevent a buyer from looking too closely. And a buyer might just not have time to research that model on the phone because of other buyers hovering over the item, or simply having to hurry on to get to a birthday party.

(Here's a fun situation: A potential buyer examining a typewriter sets the carriage lock while the seller is not looking and then offers a much-lower-than-the-asking price because the thing "doesn't work". Trickery---foul. But what if a potential buyer examines a low-asking-price typewriter and notices that the carriage lock is set and the seller just doesn't know about such things and thinks it is broken and so has priced it as junk.
I leave the determination of the ethics here as an exercise for the reader.)

Couple of points :

1.  None of my machines are "rare" and therefore do not have "Holy Grail" status.  I keep a data-base (with colored photos) of each machine with its basic data and what the machine cost me to acquire it (and maybe to repair if I had to buy parts or another parts machine).  For insurance purposes, I can "prove" my financial stake in each machine and would try to get that out of an insurance claim.

2.  Doing "comparables" on-line is an exercise in futility, IMHO.  Presently that is a decent Smith Corona "Silent" on eBay.  Typically in such condition...maybe $ 150 or so on a good day.  This one has "cursive" script...so maybe it might be worth $ 300 or so.  But its cursive script is a "vertical cursive" script...so maybe worth a total of $ 500 on a really good day.

But it's seller has it priced at $ 2,500 USD.  And then, one would really never know what the machine actually sells for...unless you happen to be the seller and the buyer.

So how would one value this offering...???