I understand your point, however Sterling's valuation isn't a fair comparison as he's English and was inflated by the whole wrangling over the deal.In a game where sterling goes for 50m mate, then rom is worth far far more than 50, James went to madrid for something like 65-70m, your talking that kind of fee easily.
Arguably he should be worth much more, unfortunately I just don't think it will work out like that if he is ever sold when you look at other deals.
Although of course I'd love to be proven wrong!