Apparently a lot of people didn't catch on since those detergents plus premiums were fairly popular. I noticed two things- didn't matter which one was used, Bonus, Breeze, Duz, Silver Dust - the boxes were the same size as other brands but the quantity of detergent was less and the usage instructions usually had you using more which leads one to believe that these products might have contained more filler than their non premium counterparts. For example - Silver Dust and Breeze, both Lever Brothers products instructed you to use 2 cups for large or heavily soiled loads, while other Lever non premium products (Drive, Fluffy All, Rinso Blue/Sunshine Rinso or Rinso with color bleach) called for 1.5 cups for large or heavily soiled loads. So either they consciously decided to really take the customer to the cleaners with the cheap quality towels and glasses along with a lesser quality product or just encouraged wastefulness with the 2 cup usage - these products were no bargain. I recall my mother used Breeze a few times (mostly for dishes and general housecleaning) and the "bath towels" in the King Size were small, thin and probably not worth anywhere what the total cost of the product ended up being.
Bonus was a relative latecomer to that lineup around 1968 or so. It was widely available in the Northeast but I don't recall that P&G ever distributed samples - it just hit the market. Of course maybe they stopped distributing samples - I don't recall that they ever did that with Gain either when it was introduced.
Anyway, Bonus wasn't around more than 5 or 6 years - then it sort of disappeared.