Assuming it is the f/4 250 mm Sonnar made for the Hasselblad 1000-series:
I have one for the 1000-series, and it, quite frankly, is not the best lens you'd hope to use. The later f/5.6 is much better. Not the thing you want to hear when trying to sell one.
But as a collector's item (and the market for this lens will almost exclusively consist of people wanting to have one for a collection), it certainly has a value that is completely unconnected to how good it is or is not. (Though for collectors more than anyone else, condition counts for a lot!)
The market isn't very large (which would depress the value), but they do not show up very often (which will make it more valuable), so it's hard to say what value that might be.
It all depends on how many people are looking for one the moment you decide to put your lens in the market.
(As an example of how things can be: some time ago, shortly after each other, a couple of f/5.6 60 mm Distagons for the 1000-series were put up for auction, and people went mad over them. Bidding went up to a quite respectable level, much, much more than i was prepared to pay for one.
A week later however, yet another one appeared. But then, the people who had been prepared to pay a quite large sum for one were nowhere to be seen, and though i couldn't believe my luck, i picked it up for less than a quarter of the price the other two had gone for. Same lens, same excellent condition, same marketplace. But apparently i was (just about) the only one not 'out to lunch' at that time.)