FN-49s here in the U.S. can be found chambered in 8mm, 7mm, 30-06, and the Argentines converted from 7.65 to 7.62 NATO. There were 9 different contracts with a total of around 20 variations. I can't say whether $649 is high or not without knowing more about the rifle.
Egyptian contract rifles in 8mm as they are the most common, the cheapest to buy, and the cheapest to feed in most cases. Egyptians can go from $300 to $800 (or more) depending on condition, originality, and what particular variant it is. You could get a mixmaster in relatively good condition for the $300 to $450 range. Century rebuilds (recognized by the beechwood reproduction stock (and usually a plastic buttplate) in good shape can run from $350 up to $550. Correct, original, matching serial number rifles can go from $350 on up depending on condition. Remember that the original finish for FN-49s is black enamel paint so if you see a rifle in some other metal finish . . . it’s not original.
Rifles in all of the other chamberings are getting pricy, and in the case of the 30-06 and 7mm, are more expensive to feed. 30-06 Luxembourg contract rifles can go from the $500 range to over $1000. The 7mm Venezuelan contract rifles can go from around $400 up past $800. The Argentine FN-49s in 7.62 chambering can go $800 easy enough (and higher).
Using the typical "collector" considerations of originality and relative rarity, my humble opinion on the CURRENT FN-49 price/availability/desirability "pecking order," listed in ascending order, would be as shown below. Pricing/desirability within each of these tiers is greatly affected by matching/non-matching and overall condition.
Parts Kit Egyptians (8x57) *
Century rebuilds (8x57) *
Original Egyptians (8x57) *
(* rifles with all original Egyptian parts would tend to be identified in the "original" tier)
Venezuelans (7x57)
Luxembourgs (30-06)
Argentines (converted to 7.62x51)
Colombians (30-06)
Belgians (30-06)
Congolese (30-06) / Indonesians (30-06)
Argentines (still in 7.65)
Brazilians (30-06)
Original sniper models (w/cheekpiece & scope)
Egyptians, Venezuelans, and Luxembourgs are the most common here in the U.S. and can be found without much trouble. Argentines show up for sale every 2 or 3 months on the auction sites. Colombians become available infrequently. Everything past that is really rare in the U.S., are not commonly available, and will tend to be pricey. No one has even seen a Brazilian here in the U.S. that I'm aware of.
If you do end up buying an FN-49, do me a favor and participate in my FN-49 survey that is running on this board at:
http://www.thehighroad.org/showthread.php?s=&threadid=10038
Also, if you do get an FN-49, you need to check and see if the rifle has a 1-piece or 2-piece firing pin. It's strongly recommended that a 2-piece pin be fitted to any rifle you intend to shoot to reduce the likelihood of slam-fires that can occur in the event of breakage of the long 1-piece pin.
HTH
Goose