How the math works
Cents per point = (cash price minus the taxes and fees on the redemption) divided by the points required, times 100. A $600 flight that costs 30,000 points plus $60 in fees works out to (600 minus 60) divided by 30,000, times 100: 1.8 cents per point.
What value should you aim for?
There is no single right number. It depends on how easily you earn the points and what else you could use them for. Count only the cash price you would really have paid: a business class fare you would never buy is not worth its sticker price to you.