Please tell me this is not standard practice! I hope there is some remedy to this other than being forced to pay double for tickets myself and others bought in good faith.
I participated in the presale for the Savannah, GA show and followed the rules just like everyone else. I selected $125 seating tickets. I was lucky and got third row seats to the show. I received this message from the ticket sellers website:

Dear John Mellencamp Fans:

Thank you for participating in the presale for the
John Mellencamp performance at Savannah Civic
Center’s Johnny Mercer Theatre on November 11th.

Regrettably, the system allowed you to purchase
tickets in the VIP seating area without being
charged the VIP price of $250 per ticket plus
convenience fees. We have two available options to
correct this error:

We can relocate you to the best possible seating
for the price you have paid, no further back than
Row K in the Orchestra sections. We will make
every attempt to select seats that are similar to
your original selection (on an aisle, on a
particular side of the venue, etc.)

If you would like to pay the difference in price
to keep your original seating, please reply to
this email and confirm that you have agreed to
being charged an additional $125 per ticket on the
credit card used at the original time of purchase.


We must receive your decision by no later than
Tuesday, August 9th at 5pm. If you have not
expressly agreed to paying the difference in price
by this time, your seats will be relocated.


Please accept our sincerest apologies for any and
all inconvenience.


Thank You,
eTix Customer Support [/i] [/i]

I believe at most we should be asked to pay half the additional cost for their mistake, not the full amount.
I would like someone from the John Mellencamp community please back us up on this one and get back with me.
Thanks, Bob