Private landowners are reaping billions of dollars in royalties each year from the boom in natural gas drilling, transforming lives and livelihoods even as the windfall provides only a modest boost to the broader economy. In Pennsylvania alone, royalty payments could top $1.2 billion for 2012, according to an Associated Press analysis that looked at state tax information, production records and estimates from the National Association of Royalty Owners. For some landowners, the unexpected royalties have made a big difference.