One of my biggest hesitations about investing in a vacuum sealer was always that if you buy a branded one (like Foodsaver, which are the only ones I ever see on sale), you have to buy Foodsaver bags for it to work which can be pricey!!!
The reason: because they need to let the air truly exit (which makes sense) but I never really wanted to splurge on bags. Well, this video found a solution!!
The trick in the video uses two strips of that special bag material to make a normal plastic bag "operate" like a special one, giving the air a path to escape. Save a little money where you can, and try this!
Note: Make sure the cheaper bags you use are still vacuum seal bags--ziplocs don't work as well because air will leak out through the (porous) plastic over time!