I'm sure the crime reached into all 50 states. Maybe they should be tried and sentenced in all of them, so avoiding jail would need 51 pardons instead of just one.
Just this week the New York Times reported the case of a venezolan banker who received a pardon after hiring a former lawyer of the president. There probably will be litigation if they misreport it so this does not seem hearsay to me.
AI readily provided me a list of 8 other well documented cases of "pay for pardons" and offered detailed research on all of them.