I keep on seeing that listing too! Actually, it really surprises me how many used lipglosses go up for sale on TradeMe, not just MAC. Seriously, who would want to use that??
We do have Back to MAC here in New Zealand, so there is really no excuse. Even if you were selling it so someone else could Back to MAC it, it's really not a good deal - lipsticks cost about NZ$42 here, so paying $10 for an empty tube isn't exactly a bargain....
p.s. Captodometer - I used to live in Dunedin, my husband and I miss it a lot!