I would agree with you, but then why are PC games usually £10-£20 cheaper than the console version?
Likewise, why can an AAA game be sold in poorer regions for £10-£20 and still cost £60-£70 here?
It's more about how much the producers are able to fleece from each market rather than actual cost. Granted there are too many games constantly coming out now so for every massive game there are probably load that lose money.
Similar, back on the Rovers shirts, yes, there is some design cost (not much looking at them) but the shirts themselves are probably made for no more than £5 each in China. I would guess there is at least 50% markup on them.