Serious 7D shooters are not necessarily amateurs on tight budgets.
Not everyone can afford to spend significant amounts of money on a camera body, or indeed lenses, yet they may wish or really need to have a given performance. Many people who earn their living from photography cannot afford 'the best' or 'the latest'. I was at a large function recently where the official photographer was using two Nikon D200 s, 2005 tech. ( With its CCD the D200 was, and still is, a fine camera).
When I was at the London Olympics I was surprised to see so many of the official photographers with ringside access using 7D s. I think someone on a 7DII thread here on CR recently said they were surprised at how many 'non gripped' Canons with pop up flash were in use at such a big event as the World Cup, so one would assume they were 7D s.
For the images that these people are producing there will be no perceivable difference between FF or crop; no one will know the difference. That situation will change in low light sports though. Will this situation change; will Canon want it to change ? This may be one reason why the new 7DII won't be 16 mp. It is one thing to offer a cheaper, credible alternate to those that cannot afford a 1Dx, but quite another to allow that cheaper alternative to compete in every sphere !
So as I have said before, the 7DII has to be significantly cheaper than a 5DIII.
The 7D is far from being a cheap camera anyway, so someone who is really 'budget minded' would be splashing out on one. However if the 7D and the 5DIII were the same price I think the 7D only be a very small percent of purchases.