In the U.S., each side usually pays their own attorney’s fees. This is called the American Rule. Until about six years ago, that rule applied to appeals from USPTO decisions. So, if an applicant appealed the USPTO’s decision not to issue a patent or register a trademark, the applicant paid the applicant’s attorney’s fees and the USPTO paid its staff attorneys their salaries. Then about 6 years ago, the USPTO decided anyone who appealed an adverse ruling should have to pay the USPTO’s attorneys’ fees as well as their own.