For me these memberships are about convenience. If I don't quite squeeze $50 worth of shipping out of them, that's fine. But they were the only place I was able to get pre-orders in for the new Retro wave, there's convention exclusives access... and occasionally they just make the most sense to buy from.
Spitballing numbers, but if I end up paying $50 for $30 worth of shipping, but it saves me some time looking for stuff, that's worth $20 to me.