I got the post-exposure series with rabies vaccine and immune globulin shots earlier this year. The total insurance charge was around $20,000 for me as well. $15,000 for the immune globulin and $5,000 for ER/Vaccine/etc. My out of pocket cost was below a few thousand after insurance, but it was expensive nonetheless.
With those kind of costs, you're probably going to hit the out-of-pocket maximum even if your insurance covers 80% or whatever which is going to be a few thousand dollars for most people. (But might be more with a cheaper high deductible plan.)