Think the $10/GB is only for post paid.
For prepaid if you use up your allotted GB, you have to buy another one month GB allowance.
Err...does Verizon even offer any postpaid plans? I thought that all of Verizon's iPad plan options were pre-paid monthly plans...
The only difference in overage charges is for Verizon's 1 GB for $20. I believe the overage for the 1 GB option is $20 instead of $10.