As a fellow poor college student (literally, as I currently have about $150/month for food) attempting to eat in a Paleo way, my advice is eat as much "Paleo" food as you can afford, but don't worry if certain foods you eat are not Paleo. Sometimes with questions like this I get the impression that people relatively new to the Paleo movement believe that the Paleo gods will punish them if they eat any foods generally deemed to be not Paleo foods, even if they are doing so out of necessity like you and I are. Your body will let you know if and when you eat foods that are not healthy for it.
When it comes to shopping for and eating food I generally follow 4 guidelines - 1)is it affordable for me?; 2)is it nutrient dense, antinutrient sparse, and well tolerated by me (my personal definition of Paleo foods); 3)eat as many whole foods and as few processed foods as possible; and 4)the 80/20 rule as advocated by most Paleo experts like Sisson and Kresser: http://chriskresser.com/food-fascism-and-the-8020-rule
This is a very relevant and important question for me and anyone else who has a tight budget yet wants to eat healthy. Coincidentally, I also love sweet potatoes, but I recommend eating the real deal and not stripped down versions of it like the noodles you mentioned. Sweet potatoes are one of the few healthy foods that are affordable for me year round, and I have found significant savings buying the largest canned sweet potatoes at my local grocery store, although whole sweet potatoes are affordable also. If you buy processed forms of sweet potato and compare the nutrition facts to whole or even canned sweet potatoes, you will see there is very little nutrition left in the processed forms (230% RDA for beta carotene in whole, 50% in processed, as just one example).
In my experience learning how to live in poverty, when you have a very limited budget for food you become a predator like our ancient ancestors were, only with the prey being foods that are already killed (I know the analogy is limited - I guess skilled scavenger would be a more accurate description). As our hunter gatherer ancestors learned to distinguish between toxic and edible plants and fungi or the least energy intensive way to hunt game, so I have learned to find the healthiest foods for the cheapest possible price at my local grocery store, and I believe anyone with a limited budget who also wants to eat healthy as you do can develop this skill over time. In a way learning how to live with limited resources is in our genes as much as eating Paleo foods.