According to a recent World Bank report, "Pirate Trails", between U$339-314M was paid out to pirates from 2005-2012. Given the low end estimate over an 8 year span, that's over U$42M/year.
According to UN statistics, the GDP of Somalia from 2010-2011 ranged from U$1067-1071M, with a GDP growth estimate of 2.6%. That works out to under U$28M/year. An obvious implication is that without piracy, the Somali economy would shrink.