You are very right about the choice according to your budget, I think it depends a lot on that, so if you have an affordable option at hand and you like it, there is no reason to go out of there. In the end the important thing is what you like, not what they try to sell you.
Besides, going out to buy your coffee, even if it's at the little store nearby, is a good excuse to get some fresh air and walk around a bit. It's all advantages.
RE: Cheap coffee, always