I have some suggestions that you might wish to consider, but it also depends ‘if’ the unit price (cost price) from the supplier is fixed for a period or fluctuates
Fluctuating unit / cost price – Trade agreements at line discount level
 To use trade agreements it would require you to enter a negative discount percentage that represents the uplift factor. Standard AX2012, does not allow for negative discounts within the trade agreement journal … however … as per a previous blog I found, this can be achieved with help from a developer by changing the extendable data type DiscPct to allow negatives. (Its an option, but not necessary the correct option)
Fixed unit / cost price for a defined period
 Create a purchase agreement for the supplier … ‘if’ the cost of the item is fixed for a defined period, then this cost (unit price) can be entered and within the purchase agreement a negative discount percent can also be entered that represents your uplift factor. You can then use this purchase agreement when creating purchase orders.