The current bid may seem high bid you have to look at all the factors. 3 full time employees (salaries, benefits, work comp ins, liability ins, etc) and the costs associated with them. The size of the facility. The frequency of cleanings. Also, the actual quote for cleaning the buildings maybe lower than the $8000. The number quoted to you might include the floor care. It might include the cleaning company supplying the paper products, too.
All I can say is do a site visit before you bid to really get a good feel for what the potential client needs & wants. Ask why the current cleaning contractor is being fired or why are they changing cleaning contractors. Ask if they want you to supply paper products? See how many people work there? Is it a high traffic or low traffic building?