That is a good point. I'm at about 100 charge cycles on mine. It will be interesting to see how the battery degrades. The RadPower bikes use stock/generic batteries so you can replace ours for roughly $400 even if you don't want to re-cell.
I'd guess for a relatively generic battery, $1 per charge is about right. For some of those fancy proprietary ones it is probably $2-3.
The cost to charge is minimal and as pointed out the cost of battery life per mile over time and ultimately the cost to change is the bottom line.
Especially as the new 20/21700 cells come online as they are not going to be compatible with existing enclosures making proprietary battery systems unable to retro fit. Nothing the bike industry likes better than a new standard however as it keeps bike sales brisk.
So that "insert price point, category and manufacturer model" here bike you buy prior to their introduction will still be supported going forward and new bikes will come already equipped as soon as next model year I for one wouldn't be in a big hurry to put down the large on an e bike at this time. But because I subscribe to the open source theory it won't be a problem to retro fit any of my bikes and I predict that "hobby" type batteries with the new cells will be the first to hit the scene.
On the other hand the new cells have been in use in the Vape market for over a year and are considered to be the standard now. Make of that what you will.....
As previously mentioned, the cost for electricity is far less than the depreciation cost for the battery alone. Even if you assume 1000 charge (30,000 miles) for a Levo battery, that's $.90 versus a dime or so for the average power bill. The bike is $5k or more. That is more than a 3 year lease on an electric car in California.