Critics of the $87.5 million investment of taxpayer money for upgrades to the Carolina Panthers’ stadium may want to avoid the annual NFL franchise values just published by Forbes. According to the financial magazine, Jerry Richardson’s franchise is now worth $1.25 billion, an increase of 18 percent from 2013. In the NFL, a league so powerful and confident in its popularity that Super Bowl halftime acts are being asked to pay the league for the privilege of performing, an 18 percent gain…