Cost Vs ET gain is directly proportional to the current e/t your running.
The faster one goes for every tenth gained, the next tenth gets more difficult.

I tried my best to pick up a few tenth in the dragster I ran but picking up 4-5+ mph at that rate takes well over 100hp to see these gains. Not easily accomplished, by even cam changes etc, especially when your already running max effort stuff. Im sorry, switching carbs, intakes,headers,cams, timing changes, tuning stuff. Not one single thing alone would get you the gain needed. More than likely all the things needed to see good e/t gains. So in my case several thousand dollars would may or may not see some return at the strip.
Where as uncapping the headers, jetting, timing changes could net 1/2 second e/t going much slower, dollars spent..maybe zero.