Heres the PPR chart,

https://proconnect.intuit.com/support/en-us/help-article/intuit-fees/proseries-pay-per-return-fees-f...

Im not sure if PS offers an additional "block" of returns to purchase at once, thats really something you need to call Sales about.   

FWIW, I think that 200 return option may be a special to new customers only, at a reduced price, so you may not get that good of a deal when you purchase more.