This is showing a lack of awareness of costs (and I speak as someone who does not own, or work in a Nursery, nor have dc there).
You are only getting £47.04 per hour, if there are 8 dc there, all day, every day.
If there are just 9 children in the room, you need 2 members of staff, but will only be receiving £52.92 per hour. That starts to make the sums look very different.
As pp has said, for a practitioner to receive £15ph, that costs the employer quite a bit more - Employers NI contributions, Pension contribution, etc, so that nudges it up to about £21ph.
You can't run a Nursery with minimum staff levels.
You need a Manager, a SENCo (who needs release time, if not FT), cover for those on courses, those off sick, those on maternity leave, bereavement leave, annual leave. You need additional people to support room staff when you have children with significant needs. All staff need training (First Aid, Safeguarding, Prevent, Food Hygiene, SEND, specifics for children who have specific medical needs, etc etc).
They also receive extra funding for children on SEN register
This is incredibly naive. This is something I know a lot about.
A very small % of children with additional needs get any additional funding.
Funding is worked out differently in different LAs, but even the dc with the most significant needs, who need 1:1 for all the time they are at Nursery, don't get anywhere near full time funding, and don't get anything towards all the time the SENCo will be spending meeting professionals, filling in paperwork, etc.
It would be wonderful for all children to be well supported, but the funding is not there for that.