Is there a package price for getting certified in all of the P6 assessments?

Yes. 

Any Two: $1,350 ($675 each)

Any Three: $1,800 ($600 each)

Any Four: $2,100 ($525 each)

Any Five: $2,250 ($450 each)

Any six: $2,400 ($400 each)

All seven: $2,450 ($350 each)

Packages must be paid in advance, and you have 1 year to complete the certifications.