How much should property management cost your condo association?

Our Condo Association Board of Directors has repeatedly decided that the condo association is better off with an onsite property manager and a combination bookkeeper/secretary. The office is open 40 hours/week during a regular week. This year, onsite property management is going to cost in excess of $100,000. We have 100 condo units, consisting of duplexes and triplexes on roughly 32 acres of land. All are ground floor units.

I have talked to several local condo associations about their costs, and they find it hard to believe we would waste this much money on a property management system. If possible, I would like to hear what other condo associations are budgeting for their management systems. How much should it cost for effective management of a condo association?