I’ve recently started crocheting, I’m on maternity leave and enjoying teaching myself. I went into Aldi last week to see they had their yarn event on. It’s apparently only on twice a year, once in Spring and once in Autumn. My local Aldi had completely sold out but the Aldi near my mum’s still had some in stock. I’d bought 8 skeins in the hope of making a blanket. I’ve of course ran out, but I’m now seeing it sold on Vinted and EBay for 4 times the cost 
It was only £1.29 in store and I’ve seen listings for £20 upwards for 4 skeins on vinted. Yes I should have bought more, but AIBU to think it’s just selfish. It’s obviously not just surplus, they’re buying with the intention to sell on for a ridiculous profit.