The sticking point reportedly is a 5- to 10-basis-point distribution and marketing fee Schwab has proposed the ETF providers pay to be on the platform. It would be similar to the 12(b)-1 fee some mutual funds charge.

The fee may seem small, especially compared with the 25 basis points mutual funds routinely charge in 12(b)-1 fees. But for the lowest-cost ETFs the levy could almost double or triple expenses. The $23 billion Vanguard Total Stock Market ETF (VTI) charges 6 basis points. The $33 billion iShares S&P 500 ETF (IVV) charges 7.

Further complicating matters is that Schwab charges only $8.95 per trade. So for some accounts, costs actually could go up, thanks to the free program.