There's more to a job than money. There's happiness. If you can get paid for what you like doing, that's something that you should be taking into consideration as part of the "total compensation" of the job. And also your current financial status, and where you want it to be. For example, if you had $50,000 in student loans to pay off, I'm betting you'd take the extra money. Most people probably would. Nothing wrong with that if you're taking into consideration the entire picture (which includes YOU).

You enjoy your job. That's great. Keep it. Don't keep it because of some heightened sense of loyalty (they likely don't have this sense towards you). Keep it because it fits your life - right now, and the future. (That's not to say you'll be in this job for the rest of your life, but that it's an appropriate stepping stone or way point on your journey.)

And don't do something you don't like for an amount of money that is simply not worth it to you. (Again, different circumstances may dictate that it is worth it, but that doesn't sound like your position.)

It's all about priorities. You come up with a set of priorities for your life, and evaluate each and every opportunity against those priorities. Where an opportunity comes up which clashes with your priorities, turn down that opportunity. Where an opportunity fails to come up to further your priorities, go out and make that opportunity happen.