You're right, however I would put myself out on a limb and suggest that, on average, you don't get many great players for free.
Additionally, the mean value of a player is, more often than not, correlated with their ability. In terms of a being a Prem player, I'd say more yes than no.
Isaak cost £125m and has scored two league goals. Gyökeres cost £56m and has scored five league goals. Igor Jesus cost £10m and scored 1.
João Pedro cost £55m and has scored six league goals. Woltemade cost £65m and scored seven. Broja cost £20m and scored 1. Delap has scored none.
Cunha has scored three league goals, costing £62m. I could keep going through, although I've hopefully gave enough examples to support my point.
Whilst he's far from the finished article, and we need him to develop further, for the price we paid his return is fairly comparable with others.