If your goal is to simply work in an ED, you are unlikely to get paid more than an EM graduate doing the same job. You are likely to be more competitive for that job, all else being equal your extra training will count.
As many EMIMs will be involved in some sort of leadership activity during their residency, this can really pay off in the long run. You would bring a unique skill set to a hospital that may be particularly valuable to them, and they would be willing to pay for it; for example if they are looking for someone to develop and run a hospitalist/proceduralist group, you may be one of the few people who can fulfill that role. Or perhaps you have been involved in research, residency administration, education... You can think of yourself as on par with someone who has done an EM residency and a fellowship.