It actually looks like Guideline is a better deal for having Vanguard funds in your 401(k) than even having Vanguard itself manage it. I can't find Vanguard's administration fees on their site (not a good sign), but they also got sued for overcharging in their 401(k) plan that they had setup with Anthem:
"Plaintiffs also allege excessive fees paid to Vanguard for record-keeping services. Over the period 2010-13, the plan paid approximately $80-$94 per participant for record keeping, both through hard-dollar and revenue-sharing fees; in September 2013, the expense was lowered to a flat annual $42 fee per participant. However, the “outside limit” of a reasonable fee for the plan would have been $30, according to the complaint."
"Plaintiffs also allege excessive fees paid to Vanguard for record-keeping services. Over the period 2010-13, the plan paid approximately $80-$94 per participant for record keeping, both through hard-dollar and revenue-sharing fees; in September 2013, the expense was lowered to a flat annual $42 fee per participant. However, the “outside limit” of a reasonable fee for the plan would have been $30, according to the complaint."
http://www.investmentnews.com/article/20160105/FREE/16010997...