If Lester would not be taking a home town discount I'd value him around 21-22 MIL a year.
The Fact that he has stated he wants to stay in Boston and a home town discount , 18-19 Ish a year would be good to keep him. Lester Is solid but he's not Cy young worthy. In fact he's never mentioned in a CY race. All the top paid pitchers in the game have CY type years minus Tanaka. Lester does NOT belong in the 25 MIL a year category for pithers