Hey Sebastian.
Maybe try to set aside the salary issue, and reflect on your interview and overall experience there. How was the workplace atmosphere? Did you get a chance to speak with any of the current employees and hear their perspective? From the limited time with your interviewer, did you leave feeling like this was a good fit for you? I wouldn't disagree with you that money plays a big factor in accepting an offer, but you should also consider other things like whether you can see yourself working there everyday and enjoying what you're doing. Hope that helps.
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Don't settle for someone who doesn't see your worth.