Not for me, but I wouldn't pay these sums for Stones right now. Let's say he has a world class season, I don't see his value rising much from what it currently is. Too much for someone so unproven at this point in my opinion.
I would also rate Varane and Zouma ( partly why I'm not so fussed about Stones staying) as better prospects, off the top of my head, and if wanted a young English prospect, i think Dier offers better value for the money that would be expected (in I feel he is similar to Stones but with less mistakes and a far lower fee would be expected) but that's just my own personal opinion.