About $600M. Just a tiny fraction of what one fighter jet costs. Works out to be about $4/worker which seems ok until you think about salary/payroll/overhead/training of an OSHA worker and suddenly that $4/worker doesn't go very far - they'd have to oversee tens of thousands of workers per compliance officer to make that budget work.

https://www.dol.gov/sites/default/files/documents/general/budget/2016/CBJ-2016-V2-12.pdf