You refer to the DAS as $100 with student discount. You need to look hard at its actual cost with student discount. Including shipping, etc.
Why do you prefer tenkeyless? If this is about health (if you currently are in pain, no matter how mild), then you getting a DAS is not an acceptable option.
This must buy now thing is the way to end up with buyers remorse. It'd be better to get whatever keyboard you can for $0 to $20 and use it for a few months, than after doing without for weeks, suddenly decide you can't wait for what you really want.
Cost versus features is a different matter. If tenkeyless is a preference that doesn't have a major impact on function, then by all means confidently save some dough and get the DAS.
If you feel like you're being forced to settle and you're the kind of person that everytime you look at your numberpad, you're going to want to hack it off, I'd recommend you wait or spend more money.
I on the otherhand, when I wasn't even using my keyboard would look at my compaq rubberdome back up (good board, which was actually meeting all my needs) would glare at it everyday and be nego and wish the eyesore replaced. It was a board, that I'd bought, because it was the only thing available and I had needed it that day. I knew it was stupid from a logical standpoint, but I couldn't change my emotional response to it and I got my Filco. I'm happy with my Filco, even though I would be better off if it was flatter, tenkeyless, had a removeable cord, PCB mounted, had different keycaps, et cetera. There's always room for improvement, so it is what you can live with.
If you don't need a tenkeyless and the timing of purchase and cost are that important, then you should be happy enough with the DAS and get the lower risk option.
If you need a tenkeyless, are a nitpicker, can afford it, then don't get the DAS.