Value of Acoustic Research AR2's

I'm looking to buy a pair of Acoustic Research AR2 loudspeakers. (Not the AR2a or AR2ax, the original AR2 speakers.) I'm not looking for something that is in mint condition or has been fully restored, but something that's original and still fully functioning. (So, it needs to sound good, but it doesn't have to look great.)

What's the range of prices I should be willing to pay?

An AR2 was my first speaker [mono system] in 1962. I can't imagine why you are looking for them; they were fine in their day but their day closed long ago. Any you find will be at minimum 45 years old [ or possibly older; the 2a came out in the middle 60s didn't it]? Good luck on finding a functioning pair; a friend found a new , unused AR 3 that had been purchased as a spare recently so anything is possible. I would go for the AR 3 myself; I had about all of the AR line in the old days as well as most of the KLH line. For something this old who knows about the price; I think whatever you pay you would be buying trouble.
I have somewhat different view than Stan above. I restored a pair of 2axs (circa 1969) that I bought last year for $100 and they sound absolutely wonderful. I think it matters that the drivers and cabinets are in good condition to begin with and that you can perform some form of restoration, in my case, redoping the cloth woofer surrounds with a latex based compound specifically for that purpose and replacing the crossover capacitors and rheostats.

They sound great and I am also a happy Thiel CS2.4 and CS 6 owner, so comparatively, these 46 year old speakers (still) provide satisfying musical enjoyment.

Worth at least $50.00 maybe.