CEX Pricing

I don't know if it's me, but has anyone noticed recently a rather massive shift in CEX's pricing ?.

Two examples - on Monday I was working out how much I'd get for a 500gb Xbox One S with 8 games. It came to around the £171 mark for vouchers and around £105 for cash.

When I went in there yesterday, I was quoted £105. And I said "Oh, that's cash, it'll be around £170 for vouchers". The person behind the counter said "Oh no, that's vouchers. It's £70 cash".

I also had my eye on a 1TB M.2 SSD to upgrade the one I have in my PC as a boot drive. Earlier in the week, they had one at my local CEX for £85.

Went in there today to debate on buying it only to find it's now £125 !.

Now I've used them often enough over the years to know they update their prices all the time, but I honestly don't think i've seen this level of increases/decreases in such a short space of time.

Unless, of course, it's me ..