I've raised this issue with my manager and they've told me that I can
transfer if i want those pay scales but that's not a possibility for me. If
the company is willing to pay me that amount in a different location, why
can't it pay me the same here?
Get another offer or several and then have this conversation again. The equation changes considerably for your manager when you are talking about leaving for a better offer. Right now he has you as an employee for a price that saves him money. When you have another offer he has to weigh losing the knowledge you have built up about the job and the business, Locating, Interviewing, and Hiring a replacement against paying you a higher wage.
