Jon -
The best way to figure what the calves are worth is to take a drive down to where you are going to market them and just watch the auction for a while. What you have to remember when you are looking at those reports is that these are usually based on grade (S,M,L and 1,2,3) and often times owners feel their cattle are better than they actually are! Then when they market them they get upset because theirs didn't bring as much as was printed in the local newspaper.
That being said - I'd say your heifer (if she's a good beef-type) is worth around $112/cwt - that meaning one hundred and twelve dollars per 100 pounds -
SO -$112/cwt (500lbs) = $560 (minus various fees charged by the stockyards.) Hope this is not too basic for you.