Charging extra for tethering is total crap—it's just another way the telecoms are trying to erode net neutrality. The fact that they charge for it makes it seem like somehow IP packets from my computer are totally different from IP packets from my phone. If they are worried about computers using more data, then just charge the correct amount for bandwidth (though honestly, in these days of mobile netflix and nice mobile web browers, I highly doubt computers use much more than phones).

Apparently some IP packets are more equal than others.

I don't know. There are some lines I'm willing to cross and feel completely ethical, and bypassing stupid arbitrary net-neutrality rules is one of them.