I actually don't think the overweight fees are all that unreasonable.

If you're traveling with 70 pounds of gear, then I assume it's pretty urgent and important stuff that you want shipped by air and you want with you immediately on the other end. If you priced it as cargo or as a Fedex next-day shipment, it'd probably cost more than $100. In some cases, a *lot* more.

Some airlines do charge by the kilogram for overweight.