He's toeing the line. Absolute rubbish to suggest that was a good price for Vidal, it's not like we got €60m or something for him (which would have been a big sum at the time) that we could put into other areas. Those were the sort of figures being mentioned for him and apparently rejected before.
It's not Allegri's responsibility to give exact reasons for why he left, but that response is vague enough to not be called what is basically a lie. What does "market opportunity" even mean in this instance?
One minute he was a vital and important player, next minute he had his choice of team for a fairly modest sum. We'll probably not know for a long time who was pushing who away, but it was probably a bit of both.