Television Commercials

It amazes me that it is profitable for companies and corporations to spend so much on commercials. There must be a lot of people out there that buy every '$19.95 plus shipping and handling' item that comes along. How can companies afford these commercials that are run thousands and hundreds of thousands times (and probably millions), if they don't average selling at least several of these items each time they are run? I know most people have car insurance, but every third commercial seems to be about car insurance - what percentage of our insurance bill is just for advertising?
I assume that viewer per television show is declining and the use of the remote to censure commercials, creates a need to show more commercials at a forced lower cost to pay expenses (might greed also be a reason?). One incentive to place ads is increased volume to make sure viewers are jolted into attention. This practice and/or a high number of commercials per hour often helps me to decide that I didn't really want to watch that program.
Many stations have started overriding the credits with commercials. I find this practice deplorable. I would think that those whose names are being rendered unreadable would protest. Couldn't the owners of these shows stipulate that the credits be shown without interference? TVLand even advertises their shows over the ending of the show in progress.
For those of us who have not completely given up on television as a form of entertainment, thank God for Ted Turner and Turner Classic Movies.