They've not unearthed a gem as in finding an unknown, but they have found a gem of a deal, I think that's what a lot of people mean.
£5m plus addons for him is absolutely next to zero risk, there's no way his value goes to zero, but a high chance it rockets up.
It's similar to Josh Maja leaving Sunderland, for 1.5m or whatever it was, when he was 19 or 20. There was just no way on earth that you wouldn't get a return on that 1.5m, as he had scored 15 in 24.
Then compare those two to, us paying 6.5m for Fletcher, who hadn't scored a single goal for West Ham, and had only scored 5 in 20 in League 1 (in 2015 when he was 20). We got him in 2017, when he was 22 and no further proven, and had gone backwards, if anything.
So compare those three, all stats from League 1:
Maja, 1.5m, 19, 0.6 goals per game (his most recent season)
Fletcher, 6.5m, 22, 0.25 goals per game (two season earlier)
Toney, 5m, 24, 0.75 goals per game (but 0.36 the season before that, 0.5 before that, 0.4 before that)
Maja probably had the most potential there (now scoring for Bordeaux), and Toney the most proven (and proving again this year), Fletcher didn't even look to have great potential and had no scoring stats to back it up either, it's bizarre.
I'm not even slagging Fletcher off mind, as I don't think he's bad at all (and showing better signs this year), I just don't think the return was likely to cover that outlay, it couldn't have ever made sense unless we thought he could be an instant success (which we didn't, as we didn't play him).
Toney is a bit older, but had been scoring goals in league 1 for many teams, since 16/17 then last year took off, it really is a good deal.
If a young lad tares it up in League 1 then buy them up, even more if they've done it for more than 2 years, there's no risk.