Hello.
I will try to explain one possible reason with an example. This is my pricing procedure - nothing really special, just to show that I have no values for calculation type or alternative base:
I will create an order for 200 PC with the same prices for PR00 and ZVP2 as you have for PR00 and ZAB5:
Everything looks great - my subtotal value shows the exact sum of PR00 and ZVP2.
I will change the order quantity to 46. Why 46? Mainly because 42 is not the answer here 
.
The subtotal shows 93.11.
The explanation: KOMV-KBETR (condition amount) of a subtotal is determined by dividing the corresponding condition value (KOMV-KWERT) by the condition basis (KOMV-KAWRT) taking into account the condition pricing unit. My only active price (I have only statistical conditions, but PR00 is still treated as the last price in the absence of non-statistical prices) is maintained per 100 PC, so the condition pricing unit is 100.
46*91.10/100 = 41.906 rounded up to 41.91 with commercial rounding - set in V/06 for PR00.
46*2/100 = 0.92
The sum of these two is 42.83 (which is definitetely correct).
The condition amount is (42.83/46)*100 = 93.1086 that becomes 93.11.