$1.5B is roughly the wage theft recovered between 2021-2023. It's estimated that more than $15B in wage theft occurs annually just from minimum wage shortfalls.
Keep in mind that wage theft is narrowly defined to include only blatantly illegal actions such as underpaying minimum wage, failing to pay overtime, requiring off-the-clock work, denying meal breaks, etc. It that doesn't even get into more general wage suppression via abusing visas, anti-poaching collusion with competitors (a favorite pastime of FANNG), and at-or-below inflation raise policies, among other things, which have caused wages to diverge from productivity over the last half century.