If you are an RN, your employer generally is not going to give you a raise if you get your IBCLC. My facility has a lactation department, and that's all they do. As they are also RNs, they are on the same pay scale as the RNs. I am an RN, employed AS an RN, but I also have my IBCLC. I don't make any more than the IBCLCs or the other RNs. Nevertheless, it's nice to have the certification for personal satisfaction and for making yourself more competitive when you're looking for employment in Mother-baby/OB.
My employer has a generous continuing education fund for their employees, and will pay when I have to recertify (and if I had worked there when I originally sat for the exam, they would have paid for that, as well as all the lactation courses I took in preparation).