Up to the owner. 750 turbine PIC isnt much leverage, or a very broad experience base for anything.
If you feel your experience and qualification makes you competitive against others who would apply, then ask for a raise commensurate with your qualification.
Be prepared before you approach management, and be armed with a comparison of your pay, comparitive worth, qualification, and know your potential competition.
If the company can hire a typed pilot with 5000 PIC in type and they're beating down the door looking for work, then that's your competition. If the only applicants are 250 hour wonders, then you're more qualified than the competition. If the company has invested in you with training and not the other guy, or needs to put less training into you, then you're ahead of the competition. Remember that you're a known quantity whereas your potential competition is not, which gives you a potential home field advantage.
Is your 250 hours turbine PIC actual pilot in command experience, or sole manipulator experience when someone else was the PIC?
If the company is presently recognizing you as PIC, then you should be paid accordingly.