Having chosen to go into business rather than a PhD (in physics) -- and then having succeeded in selling my startup, I explored going back to do a PhD. It was not an attractive option. The heads of department said I would get bored and frustrated with the politics and slow progress of the department.

Bottomline: starting a business (that succeeds) does change you expectations for "action" which will likely poison you from academia. I hypothesize if you fail in the startup that the PhD will not be an economic option at that stage!? The implication: it's hard to "reverse" this decision.