It's pretty expensive. There is a package of three one hour floats for around $100.
I would try it if it was that cheap where i live. HEre you have to pay 180€ for three hours, That is around 250$ US ....
But there seem to exist a community of floaters who have built their own tanks. This might be an option if one is desperate for a longer float. I kinda don't see the reason to try shorter floats. But paying 500$ for a real half day float ...meh, i don't know.