My estimate (I am basing this on Santo Domingo going rates) is that as a tourist or a gringo, you will pay the doc between RD$400 and $700 (US$20 to $40) for an office visit during the week, and maybe an extra RD$200 for an emergency or weekend visit.
I am not too sure of the doctor quality in Boca Chica
for $20 or $30 - unless maybe Hamaca has one in house that you can pay, I'd go to the IAMAT approved guy in San Pedro or to the good clinics in the capitol like Abreu or Abreu.