Part of the problem is that, historically, wildcat drillers must drill an average of 10 wells to find one that's a winner. Of course, the profits from that one well can easily cover the losses on the nine dry ones, and then some. But the risk of coming up dry is real. Investors in the public market just don't have the appetite for companies whose entire business is exposed to that kind of risk. And drilling costs are huge, even before the well is found.
Costs vary widely depending on the difficulty of finding and extracting the reserves.
Unfortunately for the independents, banks have been pretty reluctant to plug the funding gap. Or they're so stringent in their terms that you don't get very much money even if you put producing properties up as collateral. Another problem for wildcatters looking for bank money is hedging. That way, the bank can protect the repayment of its loan if prices suddenly drop. But equity investors in both the public and private markets oppose hedging.