Tired of sifting through 200 resumes for one decent candidate

We're a small accounting firm in Dallas with 12 employees and we've been trying to hire a senior staff accountant for 3 months now. I've posted on Indeed and LinkedIn and got flooded with applications, maybe 5 were qualified. The rest I had to manually screen and reject.

I'm spending 5-10 hours a week just on recruiting and I can't afford that time anymore. I'm thinking to go through agency.
How much does a staffing agency cost compared to doing it myself?

I just want to get back to serving my clients instead of reading cover letters.