Integration with Purchasing. Need to use modifier or formula for pricing breaks

Currently the business uses Blanket PO's for a particular supplier for only one expense item, EXP0016. The user manually changes the description for each line of the same item(various colors being ordered) and has to manually enter in the price for each color then the breaks based on the below:
Item Base Price + Batch Size Additional Cost Per Below
5 - 9 lbs. =    $10.00     per lb.
10 - 19  =   $7.50     per lb.
20 - 49   =  $3.75     per lb.
50 - 99    = $1.95     per lb.
100 - 249  =   $0.85     per lb.
250 - 349   =  $0.40     per lb.
350 - 499    = $0.25     per lb.
500+           =  $0.00     per lb.

Is there any way to use a modifier or formula to accomplish this?  I've followed doc ID 455778.1