I have attached an excel file that you can play with to see the trade-off between lowering expenses and increasing investment returns, I think you'll find the results interesting.
The scenario I've just run is a married couple who earn $100,000 per year. They currently save $15,000 pretax which provides them with roughly $65,000 in after-tax spending dollars per year. Using a 7% growth rate on their investments, some modest assumptions about inflation and taxes, their retirement account grows to just under $700,000 over 20 years.
Now, let's say this couple comes across this site and decides they want to be better off in 20 years. I give them two choices, become a professional investor and beat the markets, or reduce expenses. Which is a better use of their time?
Well, we can play with the numbers all day, but my scenario shows that if they cut $15,000 in after-tax expenses, this is equivalent to increasing their investment returns to over 15% per year. They need to more than double their investment returns! So, go ahead and customize to your situation and find out what this would be worth for you, but if your goal is to invest your way to an early retirement...good luck! Your time may be better spent learning basic automotive repair and home maintenance.