Considering that strikers cost the most, Hernandez's age, the fact that he's got the 3rd highest goals per 90 minutes rate in Prem History (behind Thierry Henry and Aguero, though Suarez and Lukaku look likely to pass him at the rate they're going at) his lack of injuries and his fantastic scoring rate for Mexico (35 in 58), I definitely think someone would offer 20million for him.
It's hard (although doable) to go down with a 20 goal scorer, and give Hernandez 35 starts alone up top and he'll hit that mark.
Looking at strikers coming to Prem teams last summer and January, Negredo and Jovetic went for 25 and 30, Soldado for 25 I think, Bony went for 12 million, Long and Jelavic went for 6-7 each. I think Hernandez for around 20 looks right to me, maybe even a few million higher if he scores a couple world cup goals this summer.
Not sure it will be a Prem team, though, unless Martinez can't get Lukaku or Wenger realizes Hernandez would be worth 20 million even if he was only splitting with Giroud and getting goals off the bench, feasting off Ozil, Ramsey and Cazorla through balls.
When you consider how many strikers, like Berbatov, struggle to score off the bench, and how often strikers get chucked on to the pitch and asked to get a goal in the last half-hour...
I wouldn't be shocked if a top continental team was willing to pay 20 for Hernandez, considering that he opens up the Mexican market, too.
I could see him being Costa's replacement at Atletico Madrid (with the 20 million or so profit on that trade going to their debt and keeping other players) with how hard he works, or going to Real Madrid if they don't rate Morata, as the backup 9 to Benzema, or to Monaco if Falcao leaves.
I absolutely love Chicharito.