Definitely more than a HJ but from my experience, "huge boobs standard service" typically isn't cheap.
Just to give you a frame of reference, here's a provider I see from time to time with unreal tits:
Her rate is $600 [which increased recently for new clients] but she's young, funny and literally open to EVERYTHING.
Basically, you'll stumble across diamonds in the rough from time to time but busty girls [especially with big natties] usually tax.