They sell a $25/vial of Regular insulin; its an older style, and can be fairly dangerous to use, as it has quite the different action as the newer 'fast-acting' insulins.
With that said, if tight on money, its certainly better to use it, and monitor it closely, than not be able to afford the $225+/vial novolog or humalog.
It’s not “fairly dangerous to use”. Unlike aspart, Regular is less potent and has a slower and longer activity profile. If you have poor food absorption after a meal, take the wrong dose, or have any other event that would change your insulin requirements, you will find yourself in much sooner trouble with less time to react from aspart versions.
Walmart sells their own brand for about $0.20 each, the "name brand" ones are about $0.60-80 here. I have a diabetic friend whose insurance will only pay for 2 strips per day and he buys the remainder from walmart (and has 2 meters because the insurance-provided one is a different model that doesn't work with the walmart test strips).
With that said, if tight on money, its certainly better to use it, and monitor it closely, than not be able to afford the $225+/vial novolog or humalog.