Petrobras´ market value is nearing $250Bn which is fairly high but if (the key) is ´the cash costs of the deep sea oil per barrel. PBR is spending at least $174Bn to develop this (one of the largest capital projects in history, ever).
I did a quick calcuation of the payback period of the deep sea oil costs. The estimate is that initially the deep sea will produce an additional 2 million barrels of oil -- quick calculation, assuming a profit per barrel of $40 after direct operating costs = $29.2Bn of profit per year, or a 5.96 year payoff period -- this is at the high end of aceptable levels of payoff, in which oil and gas firms want payoffs to be below 5 years.
If the profit after operating costs is $60, the payback period drops to 3.94 years. Need to find better data on direct operating costs. If it is only costing PBR $20 to hire workers, equipment, power, water, foodservice etc then this isn´t bad at all (since the deposit is likely very large and will last for decades)(the price of oil should be in the $70-90 range for a while).
One more note: I did find data that at least at Tupi the gas/oil ratio is 15-20% -- majority oil (perhaps the pressure maintains the longer hydrocarbon chains). In geological theory, the deeper the deposit, the hotter and the more the longer hydrocarbon chains will have been broken to form natural gas, but PBR seems quite confident the deposit is mainly oil (of course natural gas is cheaper currently and less profitable and also is much more difficult to transport from offshore locations).