I think it is a bit of a slippery slope to start breaking it down like that - because all children will incur a different cost on a center - e.g. nappies (some may need till 3.5 some only till 2), through dietary requirements (for allergic or religious reasons for example), some children require more attention than others (and staffing decisions can be impacted by that), babies need a higher staff to child ratio than older children, some mums provide breastmilk - some use the centers formula etc etc.
True! Maybe I'm just being too pertnickity!