What confuses me is arsenal fans believe keeping him is a guarantee to top 4. It wasn't last season and it's no gurantee he'll get them there this season with the other teams looking really strong. Can they afford to miss out of champions league two years in a row AND lose their best player on a free instead of 50 million?
I don't think any Arsenal fan i know thinks it guarantees top 4, but it does increase the chances.
Wenger is in a no win situation here. Pressure is on him greater than ever before, and he knows he doesn't have long to go.
Of course keeping Sanchez is a gamble, but he knows what Sanchez can do on the park, and that's more guaranteed than what any replacement can offer.
It's not just about transfer fee, it's about trying to get back into the Champions League, helping to attract better players, keeping the current players, his image with the fans, a potential lucrative kit deal up for renewal next year, secondary sponsorships etc.
As for Kronke and the board, I can't believe the strategy wasn't spoken about during Wengers renewal. Whether that was to deny a transfer, or to sell at a set fee.... we'll soon see.