I would definitely agree that there is a social benefit to trademarks (much more significant than that of patents or copyrights).

I don't think I object to the cost in the general sense, from the registrant's perspective. But from the other side, the registries have the potential to make a decent chunk of change off this, which really feels like they're making money not for providing a useful service, but by exploiting features of trademark law. It just feels a little dirty to me.