It's a lot of money, especially with the whole pandemic going on but Sancho can give us 10 very good years, minimum. And since he doesn't rely on his pace too much, he can easily play into his mid 30s IMO. 100 mill for 10-12 years of top tier performance is not bad IMO especially considering the potential this guy has.
All the successful teams have a talisman, a star player, players like Rooney, Ronaldo, RVP, Aguero, Hazard, Salah, players capable of winning games all be themselves. IMO we lack such a player. Martial and Rashford are too inconsistent, Bruno has been here only for a few months and Greenwood is young. They all have the potential but I think Sancho could be that player for us.