I don't think it's an overpay at all if the rumored 60m fee is accurate. Tel is a VERY promising player with skills to contribute now. He'd be the heir apparent to the LW role if he's brought in permanently, and is almost certain to be in demand down the line by the biggest clubs. Even if this whole "youth experiment" fails, we can make bank selling Gray, Bergvall, Vuskovic, Tel, etc down the line.
All that being said, this smells too much like the Luis Diaz move. Feels like we're being used to get terms and then he can say "match it" to the clubs he wants to go to.