Hm. Well, if you have the option of $40k and no degree, and $55k-$60k and a degree, I would stick it out. IMHO it would be a mistake to allow your own feelings on the value of a college degree weigh too heavily on this decision. I say this because there is a lifelong advantage in having it. You personally might not be convinced that it is worth an extra $15k in debt (and the arguments on that side are convincing), but believe me, many people do feel it is. Rather than having to be the guy that "was successful despite not finishing college", you don't have to weave that narrative into your future endeavors, whatever they may be.

One year from now, you can walk away with the degree and say: "What a waste that was!" And, even if you feel that it was a waste of money in your heart of hearts, and even if you tell people that you feel this, they will see you differently. They will see you as someone that finished what they started, and then moved on, and I am not just speaking of employers. IMHO you will feel better closing the book on this with the degree in your hand. You will carry less doubt with that decision, and people will see less doubt.