Ay, congrats sa pregnancy po! I haven't personally done a Hep B booster during pregnancy, pero I think you should really ask your OB directly about the cost kasi it can vary depending sa clinic or hospital, some might charge 500-1000+ pesos, pero mas makakatipid ka if it's covered ng insurance mo or if you get it sa government health center. Better to confirm din with your doc kung talaga bang kailangan mo ngayon or pwedeng after delivery na, lalo na kung vaccinated ka na before.