Ask a Fool: What Do $0 Trading Commissions Mean to Investors?
Like you alluded to, the move toward zero commission stock trades is likely to save stock investors a significant amount of money over time. If you buy stocks once a month, the elimination of TD Ameritrade's (NASDAQ: AMTD) $6.95 commission will save you more than $83 per year.
However, that's not the only reason this is a big win for investors.
In addition to the savings, this makes it easier for investors to put smaller amounts of money into their favorite stocks. In other words, let's say that I have an extra $100 sitting in my brokerage account and that I'd like to add to my Bank of America (NYSE: BAC) position.
Source Fool.com