No, that's definitely not right. Encryption will make the data larger, but that's only because encryption algorithms usually have a fixed block size to deal with. For 128-bit encryption that block will be 16 bytes, so whatever you send will be scaled up to the nearest multiple of 16 bytes--e.g. to get a 128x inflation of size you'd have to be sending a single bit of data, which doesn't seem very likely! I wouldn't expect an overhead of more than a couple of percent in most cases, and I don't think anyone would ever use a VPN if that wasn't the case.