An interesting concept but I have "only" bought 10 so far and did so with a view to keeping them (or wearing them out). I picked each one because they were my clan tartans, or because I really liked them, some were expensive and some very cheap, but they all met a want (I hesitate to say need). While they still fit or have the potential to expand with my waistline, I would hate to sell any of them.
They generally get worn but I have not plucked up courage to set off around Ireland in Loud McLeod yet.