The Invergordon Mutiny and pay harmonization

Does the Invergordon Mutiny prove Britain could no longer afford to pay the Royal Navy?

No. It followed a badly handled attempt to equalize pay scales downward rather than an inability to meet the payroll.

The proposed changes attempted to harmonize different pay scales downward. Sailors resisted because the policy imposed unequal losses and was introduced through exceptionally poor personnel management. The episode was a labor-negotiation and administrative failure that senior naval intervention eventually resolved. It does not prove that Britain lacked the money to meet the Royal Navy payroll.