It also cited the potential problem of a two-tiered market in which market makers quote one price to public investors while quoting better prices in private systems , thus robbing investors without access to " hidden " quotes the benefit of the best available prices .
<response> It also cited the potential problem of a two-tiered market in which market makers quote one price to public investors while quoting better prices in private systems , thus robbing investors without access to " hidden " quotes the benefit of the best available prices . </response>