The first method – Do not set the pricing condition VPRS as a statistical condition type. Simply remove PR00 and it will work fine if you always use VPRS as your pricing base inside the pricing procedure. VPRS will read both prices based on the price control in the material master. 

Price control S for standard price. 
Price control V for moving average price.   

However, if you are using one pricing procedure where for some items you price using VPRS and some others using PR00, then you should use requirement routines to enable the correct price condition type at the right time. 

The second method involves more work as you need to write a formula ( VOFM) to get that information. 

This is how it goes :- 

1. Set VPRS to be the first step in the pricing procedure and to be subtotal B (as standard). 

2. Set PR00 with alt. calc. type formula, which sets the value of PR00 to be equal to the subtotal B. 
    The routine (created with transaction VOFM) is: 

RV64A901
FORM FRM_KONDI_WERT_600. 
    XKWERT = KOMP-WAVWR.
ENDFORM.

The pricing procedure than looks like that: 

Step 1 VPRS statistical, subtotal B, reqt 4 
Step 2 PR00 Altcty 600