1) I have seen several FMAP M1927's lately, including Air Force and Navy versions, offered $500 to $600 but not selling very quickly. This is for the arsenal refinished ones that came in during the 1990s. A "market clearing" price is probably $450 to $500 for these type guns right now.
2) To get an accurate estimate, you need to state whether it's the original blue finish from 50 odd years ago (rare) or an arsenal refinish from later (most common). The latter is worth less.
One thing to watch out for on Argentine military pistols is breechface damage. I have seen several that were apparently stored in the armory on racks holding pistols by means of a steel rod passed through the muzzle. Some of these rods apparently had no pads or protectors on the ends and peened the breechface badly requiring slide replacement. But if you find a nice one they are really nice examples of a 1911 built of very high quality steel with amazing heat treatment. Most of them show little or no wear from firing. The finish will probably be gone but that's easy to fix. I would be wary of buying without a close inspection.
I have a Ballister Molina Argentine surplus .45 I picked up about 15 yrs ago for $140. Interesting handgun. Browning action, no grip safety. Put a government barrel in it, bobbed the trigger and smoothed it up. Now my wife shoots it. It's pretty reliable but I doubt it's worth all that much.