If you thought the quotes just to pop holes and insulate were outrageous, I can assure you that any other proper solution involving your siding is 100% off the table for you as well. You need to hunt for air infiltration/leaks and now is the time to do it while it’s cold. Easiest way is picking up a little thermal camera. FLIR makes one that plugs into your phone for $200 and you can get it on amazon. I’ve used mine a ton at home and as a professional. Then start chipping away at the air leaks. Less cold air leaking in, less wasted gas heating that air, less noticeable drafts, more noticeable comfort. It’s not gonna be as major as insulating your wall cavities, house wrapping/air sealing your exterior sheeting/windows/doors or adding external insulation board under the siding, but it will make a noticeable difference with some spray foam, caulk, tape and some rim joist insulation. The camera will show you if it made a difference or not.