Alternatives to sewing machine bobbin felt pads I saw a sewing machine tutorial where the repairman said some problems can be prevented by using sewing machine bobbin felt pads.

Two felt pads came with my Singer Start 1304.

Now, one is missing.

Amazon lists a crazy price of $6.99 for a pack of 10.

Are those felt pads really necessary?
And do they really have to be that expensive - is there a cheaper alternative to using Bobbin Felt pads so that it protects the sewing machine from any damage?
Bobbin pad? Or spool pad? I use spool pads to protect the surface of my antique sewing machine (1940's Singer Featherweight). Different shaped spools can sometimes rub on the surface around the spool area. I didn't use pads when I had a modern machine. 

Sometimes your thread might come on a different sized spool or a different size of hole in the middle, and a felt pad can help a spool with a larger hole sit better on the machine, and keep a constant tension instead of jumping around a lot. A friend's machine is very touchy about how it is threaded, and for shorter height spools a pad helps align the thread more with what the machine likes.

I bought my spool pads on Etsy and they are 100% wool and 5mm thick in a variety of colors. But you could likely use any felt.