To be really safe, we each need around 2-3 bottles from C3 to C4 (including sleep), 2 bottles at C4, 4-5 for the summit push and two spares. That totals 12.
If you are up for another attempt you need at least another eight. That totals twenty bottles.
The cost for this will be around US 300 each bottle or US 6000 in total. Invest this money and sell what you are not using upon going home. If you want, you can purchase cheaper bottles for the use at camps/sleep.
Check prices at www.poisk-ltd.ru/