Originally Posted by
Abu Mahendra
Assuming, on tour, in a day the wheels spin for five hours, the powerbank is equivalent to four days riding on a dynamo hub. The powerbank costs $20...
I do not do four day or similar length tours. But if I did, you are right. That is a very good price, the last power banks I bought had one fifth of the capacity you cited, yet cost $25 USD.
It is really nice to not have to worry about searching out where the outlets are in a restaurant and hope that a seat near one is unoccupied if you stop for lunch on a tour. I did a two week tour a year ago, first tour where I was self sufficient and did not have to worry about searching for power everywhere.