Alot of the time centres charge more for babies than for older children, due to higher ratios and a higher level of needs of the babies.
As far as I am aware, there is no governing body on what fees are in certain areas. Each centre dictates their own needs in the area of fees. As long as it is reasonable. Perhaps ask the director and point it out to them the differences in prices and what they provide. I know around my area (in sw sydney) there is a pretty big difference in childcare fees. Council centres are all very similar and are based on what is provided- ie nappies/food, but private centres and community based centres have big differences, sometimes up to $10-15.