The expenses will be reimbursed by the public purse.
Tips
register
Slightly old-fashioned / colloquial. In modern formal writing 政府 or 国家 is preferred; 公家 still appears in everyday contrasts like 公家的 vs 私人的 ("belonging to the state" vs "belonging to a private individual").
history
In classical texts 公家 referred to the ruling house or imperial court — the modern "government / public" sense is a republican-era extension.