That seems like it might be a bit on the high side, but it's hard to tell without more information.
As an example, if the rents were $1100/month on average *12 units*12 months = $158,400 in revenue before vacancy.
27,000 / 158,400 = 17% of revenue for management.
As others have mentioned, you haven't provided enough information to determine whether this is good value or not. If it's in a high rent small town with rough clientelle and only one active management company, then the going rate might just be high.
Regards,
Michael