If it is the chart you are referring to I believe you are mistaken. Think of pH as the output. I know the chart looks like if you change any of the variables the CO2 will change, but this isn't how it works because both other variables will change at the same time. If you simply increase kH, your pH will go up as well. And if they both increase you won't actually be getting more CO2.
If you have a higher kH for instance, it will take more CO2 to get the same change in pH than if your kH was 4 for example. After all kH is buffering through carbonate, so at a higher kH it is easy to see that it takes more carbonic acid to reduce the overall pH.
I think Tom Barr said it best "The only way to add more CO2 is to add more CO2."
The chart is just a way for you to determine how much CO2 is in the water given your kH and current pH.
50g tank has a Griggs reactor and 24oz PB tank.
I have halved the CO2 output from 3bps to 1.5bps (large bubbles), and everything is still bubbling and pearling. Fish respiration is normal. Today, pH is 7 as opposed to 6.6 before. At night it goes to 8.1. IME, raising KH 3 points using AB only raises PH .1 point.
My observation is that the extra Alkaline Buffer I have been adding, is much less expensive than the cost of extra CO2 and saves me trips to Dick's for refills.
If I keep the tank set up as is, according to the chart, I am at 30ppm and using just half the CO2 I was using before. Which means I will get 2 months from the PB tank. If I decide to run at say 15-20ppm, I will possibly get 3-4 months!
My point is that it costs much less to keep Kh high than it does to keep KH low and use 2x the CO2. Also, the PH stays closer to neutral and is possibly less stressful for fish.