Manchester United are rumoured to be interested in Ollie Watkins transfer this summer. Honestly he is one of the reasonable players to be targeted for the attacking line. However he won't be a cheap transfer at the same time. He is having his most productive season at Aston Villa now (19 goals, 13 assists in the Premier League). His current market value is 65 million euros.
Aston Villa can make a huge profit from a possible transfer. They signed him for 34 million euros 4 years ago. They know how keen Manchester United are about spending a lot of money for their targets.

I don't expect Aston Villa to price him less than his current value.