here in ny, I've seen them as high as 20. the nicest ones I've gotten though, were 6 bucks each, and have a lot of white. the one female who's bred is beautiful, probably a low "S" grade with a lot of white and "eyes" on her back, and her 10 kids all have really defined, solid white areas, some with eyes as well... some of the males are rather dull though, with partial white and some faded red... so I have no idea which one she mated with. she's mated twice since I set up the tank, what in february. I haven't seen any fry from the second berrying though, I think I may have sucked them out in a huried water change one night, when I saw the temp getting high, around 79. I try to change the water whenever I notice it's warmer than 77. (usually twice a week or something, about 1 gallon change)
anyway, I'd say, if the shrimp look nice and have a lot of white, go for it. get 4. they are certainly cheaper through hobbyists, I'll probably even sell a few in the summer... but you can't see them before you buy them. if the ones at the store are faded, or just aren't stunning... then hold off.
try and get as many female as you can, once you start paying attention to the shape differences, it's not so hard to pick them out. you need at least one.
http://www.planetinverts.com/crystal red shrimp grading guide.html