I can pretty much tell by how expanded they are, etc. If the polyps do come out, how large should they be. The polyps should extend after an hour or two of lights out. The healthier the colony gets, the ealier the polyps come out. If very healthy, the polyps part- ially extend during the day.
Some species always extend polyps.
The price is dropping and it all depends on the wholesalers price and how much the retailer jacked it up. These are southern cal prices which might be lower because of proximatey to wholesalers. Follow my above suggestions and everything should be fine. You could also look for acropora eating snails and worms at night with a flashlight. My main reef now has 33 species of which 29 are whole colonies.