Very early days. We should always have an idea what his value is though.
Before we start fantasising about megabucks remember that West Ham paid 20 million for Bowen, who had 50 odd goals to his name by then. Villa paid 28 million for Watkins after he had about the same. Both were unproven at Prem level.
Also worth bearing in mind the Blades paid 20 odd million for Brewster after he scored just 10 goals for Swansea(!)
So if an offer of 20 million comes in before he gets 50 goals, maybe you consider it.