That seems to be the target with Delta lately ($35-50)/hour for an FCM "upgrade". It's interesting with forums such as this, published data on profits, and just general data that is available to everyone, how easy it is to see how much every consumer's activity is worth to a certain company.
In this case, $35/hour during flight time seems to be Delta's tipping point where brand loyalty is appreciated, but additional ancillary income is worth more to them. Granted, this is WAY oversimplifying the equation here, as a lowly FO as myself is not treated with the same consideration as a DM.
Similarly, this is exactly where the offer stands for our flights to DSM this holiday. $151 RT for each passenger works out to about $50/hr. Absolutely not worth an additional $600 for the family of 4 on a 1.5 hour flight, but would definitely have done if it was just me or even the wife and I.
Be lucky,
LJ