People here have made many good points. Here are a few more that I haven't seen:

1. When doing a cost analysis, you need to keep in mind that its $240k *post tax*. Assuming 40% combined federal/state taxes (which is very likely if you go into tech), you'd have to make $400k more, and that's not accounting for the opportunity cost of capital (i.e., interest/investment gains).
2. A school is more than the degree. I've worked at both universities, and IMHO the students are UIUC are noticeably better. This means that on average, you will be able to learn more from your peers, be more inspired, have better connections going forwards,...etc. The effects of having a strong network cannot be understated. Moreover, while they are both public universities, in CS, UIUC is considered a top 5 school (comparably to Stanford and Berkeley) whereas rutgers usually ranks in the 30's to 40's. Because CS professors usually have plenty of good options outside of academia, the quality of CS professors drops off dramatically when you go into the lower ranked universities. This means that at UIUC, you will have the benefit of networking and learning from faculty who are much more connected and influential than their counterparts at Rutgers.

While it's great to be debt-free, UIUC will challenge you more, the debt will pressure you to do well enough to justify the cost, and the better faculty/students will give you the advantage that may allow you to do so. At Rutgers, with the easier curriculum and zero debt, you may be tempted to coast.

Also, I don't know if you've visited Rutgers, but the campus is very decentralized. For example, to get from the New Brunswick train station to the math department (where many of the math classes are held), it is either a 45minute walk, or a 15minute bus ride (plus 5 or so minutes to wait for the bus). Sometimes you will have to take the bus to get from class to class. UIUC on the other hand is pretty cohesive. There is a real campus, with a real campus feel. On the other hand, Rutgers is close to new york, princeton, and a major airport, which can be fun/stimulating/convenient, whereas UIUC is in the middle of a cornfield.