School nurseries and private nurseries are funded differently. School nurseries get more per hour per placement. Schools don't need to pay VAT like private nurseries do. Comparing private nursery with school nursery isn't an accurate representation.
Under 2 are 1:3, 2-3 are 1:4, 3 and above are 1:8 however this doesn't take into account enhanced ratio needs for SEN.
Nurseries need to pay staff, rent/mortgage, insurances, ofsted registration, training fees, admin (computers, tablets, printers etc), run cars if doing before and after school provision or for trips out, resources and toys for the children, equipment such as climbing frames, food, food hygiene certs and training, cots, tables and chairs, buggies, books, utilities, caring for garden such as new plants, mowers etc.
My point is there is a whole host of hidden costs in running a nursery and the funding the government provides isn't enough to meet all these costs which is why many small independent nurseries are closing or concerned about running costs.