If I set my thermostat to 78F the AC would almost never turn on, so forget about getting any dehumidification. It would be unbearable, especially trying to sleep at 82F.
Lately I've been keeping it around 74-75F 24/7. Usually 75F is OK on the weekends as the indoor humidity doesn't get much above 50%, but I prefer it more in the mid-high 40s.
Throughout June/July I actually kept the temperature at 71-72F and my bill spiked pretty high - 352kWh in June and 614kWh in July (though it was a very hot July). Add a dehumidifer running in the basement and yeah. Still probably low compared to a lot of people, though. This August's usage will probably be around the same as last August, ~417kWh.
EDIT: If my winter usage is shocking, it's probably because I use propane for heating/water heater. Over the past seven years, I've been averaging ~1.5 fills per year with a 500 gallon tank, which has come out to ~$100/month if spread out over 12 months/year.
Maybe those temps are OK if you live in a very hot climate like Texas so your AC is running more often, but in the Northeast it would be crazy. You'd probably be lucky to get one cycle every 1.5-2 hours with a well-insulated house.
What's their winter recommendation? 55F when home, 50F when sleeping, 45F when away?