I think the term monolithic is being used improperly here. By definition, it just means you will pour said slab in ONE pour vs multiple pours.
Typically construction joints (break in pours) is done for the convenience of the contractor and does not affect overall strength as long as your reinforcing is properly done. In fact, multiple pours is required in our line of work so that beam loads are properly dispersed when pouring the bridge decks.
What you are really asking is can a slab with thickened edges be acceptable in lieu of a traditional slab with true concrete footer. If it was mine, I would do a real footer, end of story.
No idea what residential guys are charging for their work. My company does bridges, and with our form work, labor, etc we have higher costs I imagine. For materials & labor, we range $400-600/cy depending on specifics.