I travelled on a Star Alliance ticket. There was no charge for schedule changes as long as they were made at least two hours before the flight. There was a $100 charge for re-calculating the ticket and no refund given for any possible savings in the re-routing of the ticket including airport taxes that had already been paid. In my case, I had a ticket that was going to allow me to fly on some of the final legs of my ticket capetown-frankfurt, cairo, madrid, nyc, toronto, vancouver and I changed it to jo'burg-frankfurt-west palm beach-toronto- vancouver. Re-routing and recalculating an RTW ticket is a lot of work.
The cheapest RTW tickets go from hub to hub and are limited to five or six cities. Its then up to you to travel around that hub and back again. i.e. Delhi, Bangkok, LA, London are all hub cities.
If you book/buy an RTW ticket, I'd suggest you only book the first few flights and the last flight. Leave the other flight dates open and book them a couple of weeks in advance as you go.
Remember that most RTW tickets are a lot of work. Don't screw your travel agent by making them and the airlines do a lot of work for nothing. Use them properly and they can be exceptional value. I think I had something like 23 flights for around $6000 CDN.Then I booked a few more in China, Australia as well as SEA to and from India that could not be accomodated on the RTW for another couple thousand. (at the time this would have been a total of $5200 USD)
If I had to do it again, as a North American I would fly to London and buy my ticket there. The cheapest RTW's depart London or from Down Under.