The above video I made on the fly the other day in the shop while I was working on a brake job.
The difference between $40 brake pads and $90 brake pads is night and day. The $40 pads will almost never come with shims, and hardware like the more expensive pads do.
And the recipe that the $40 pads are formulated with is most likely generic and not built to the particular vehicle that they are going to be installed on.
It means they might not work as well as the brake pads that came on the vehicle from the factory. But they will stop the vehicle. So they are better than nothing. But if you want the most performance from your brakes, buy the best brake pads you can get. They last longer, they make less noise, and they cost less money per mile in the long run.
When you bring your vehicle to us you never have to worry about getting cheap brake pads; we always install the best brake pad available on our customer's vehicles. The premium pads we use are custom formulated for each specific vehicle. Because you never know when 10 feet more stopping distance is going to be the difference between life and death.