That wasn't helpful at ALL
true

and shows a clear misunderstanding of elementary Economics.
on the contrary...
Stuff doesn't just "have a value". The current market price gives the Spacesaver a current market value (depending on the condition). But that is not "the value" of the Spacesaver. In other areas of the world, the value would be totally different. In other areas of the market (old office building where no one knows what a Spacesaver Model M is and hence has no idea and/or interest in finding out what the market currently pays for it) the value would be totally different.
Point I was trying to make is that the OP has to decide for himself what value an IBM Model M Spacesaver has TO HIM. And THAT is what he "should" pay for it.
To me an IBM Model M Spacesaver would have a value of roughly 40€ which would be a little more than iMav paid. I came up with that price by considering stuff like missing NKRO, Windows keys, etc. while on the pro side adding stuff like oldschoolness, build to lastness, etc.
Value to me might increase considerably once I actually tried an IBM model M which I can get for 30-40€ on eBay here depending on the condition.
The current market value of Spacesavers in the US with over 130$ going to over 200$ depending on condition is way off in correlation to "my value". Thus if I was interested in buying it, I'd defo say "I shouldn't pay that".
I think a good way to find out the "personal value" of a product for thineself is to ask yourself "what would I pay for it?". Don't fool around and say "a buck, haha!". That leads nowhere. I usually go by "what alternatives do I have?" for example a Filco Tenkeyless. Then I check what it costs at various places. Maybe look at it over a certain period of time and can see that around 120€ is probably the lowest I could pay for a Filco Tenkeyless.
Now the question is, is a NIB Model M Spacesaver worth to me as much as a Filco Tenkeyless? Depends, to me no, to the OP, maybe yes. Depends on how much u value the buckling springs and how much u value the "tenkeyless" aspect. Let's say you highly value the BS but only moderately value "tenkeyless". Then you should check how much a normal NIB Model M goes for. Let's say 50$. As you only "moderately" value the "tenkeyless", you would be getting a personal value of the Spacesaver Model M between 50$ and 120$.
If you highly value both BS and tenkeyless, then there is no question, you just gotta pay what the market demands. One factor in this would be time, if you have it, you can wait. Speculating that either prices drop in general or that you somewhere, sometime get that "deal of a lifetime".
I guess you can fill in the blankes in regard to other "valuation processes", like considering other alternative boards, valuing "tenkeyless" highly but BS only "moderately", etc.