Digital BW, The Print

So,I tried to calculate the costs of  photo  prints done with an Epson
1280,with an continuos flow system,MIS Variable Quad Inks (for cool or
neutral tone prints),on 11x17 Sommerset Enhanced,considering that 4 0z
bottles = 12 reffils = 240 prints  (assuming 1 standart cartridge can
produce 20 prints) Final cost per photo came out to be U$ 2,87 (paper +
ink).Does is seems correct? Any comments or corrections on my thoughts?
Below is the spreedsheet:

      Sommerset Enhenced SV1117PE-25 25 sheets     11 x 17 $63.00  Each
sheet  Cost per photo
           2,52

      MIS VARIABLE MIX HEXTONES - 6 Color Printers

      4 Oz bottles(113 ml)
      VM-HEX-4-C 4 oz VM Hextone - Cyan Position $12.00   Total  2,87
       VM-HEX-4-VM1 4 oz VM Hextone - Magenta Position $16.00   84,00
       VM-HEX-4-Y 4 oz VM Hextone - Yellow Position $12.00
       VM-HEX-4-PC 4 oz VM Hextone - Photo Cyan Position $12.00   Each sheet
       VM-HEX-4-VM2 4 oz VM Hextone - Photo Mag Position $16.00   0,35
       VM-HEX-4-K 4 oz VM Hextone - Black Position $16.00


      Continuos Flow System for

      Epson 1270


      CFC-1270 $54.90


      MIS-AG1270 $37.00


      Total 91.90






Andr\ufffd Vallejo
avs@...
Niter\ufffdi-Rio de Janeiro
Brasil
Galeria de fotos-> http://www.fotografia.em.pt/lista_temas.asp?autor=4652