I recently read a workgroup investigation on ICANN website. They were investigation domainstasting problem. To my surprise, I learned that ICANN fee of $0.25 is NOT charged for tasted-and-deleted domains. Therefore, it is still free (and was always free) to "test-and-delete" domain name... of course it is free for registrars.
Furthermore, I learned that almost all registrars do NOT deposit real funds to the registries before the registrations, but they obtain a line of credit insead... and actual funds are deposited AFTER the registrations occured, only for those regs that were not deleted during the grace period!