The most expensive country is actually Iran, which levies 500%! Yes, your carnet issuer really will require a bond/guarantee for that amount.
You do indeed definitely need a carnet for India. I managed to leave India this year to Pakistan without one, but I've never heard of anyone entering India without one. Indeed, there are many vehicles at the India/Pakistan border that were abandoned by their owners when they couldn't get them into India without a carnet. The Indians are well known for being sticklers on this point.
India and Nepal have a reciprocal arrangement for use of vehicles in each other's countries without the need for a carnet. For entering India from Nepal, I believe it is necessary to leave a deposit with the Indian embassy in Kathmandu, which is returned when you re-enter Nepal. Going the other way, I think there's a daily charge. However, unless you bought your bike in India or Nepal, this wouldn't be much use to you, since you'd need a carnet to enter either country in the first place.