It $20 per year for an individual 401(k) account (commonly used by owners of small businesses).[1] One could assume the rates for regular employer 401(k)s are similar.
That's slightly less than Guideline's 0.03% fee, for accounts with large balances. A $100k account would pay Guideline $30/year, and a $1mil account would pay $300/year. Although most Americans probably don't have that much in their 401(k)s.
Considering a lot of people will have low balances, Vanguard and Guideline cost almost the same.
I think the decision for a small business now comes down to just three factors:
1. Does Guidelines have a better website/app user interface, and better customer service?
2. Vanguard is a well-established company. Guideline is small and new.
3. From the business side of things, is Guidelines easier to work with compared to Vanguard? I.e. with things setting things up, adding new employee accounts, etc.
I'd go with Vanguard just based on factor 2: because they're well-established and fairly trustworthy, and being investor-owned, they're not trying to profit off of their investors.
