There are some giant flat fees that ICANN charges to be a registrar:
> What you will pay to ICANN:
> US$3,500 application fee, which is non-refundable regardless of whether the application is approved, denied, or withdrawn. Following an initial review of completed application materials, ICANN will contact applicant with instructions on how to submit payment.
> US$4,000 yearly accreditation fee due upon approval and each year thereafter.
They also require you to prove that you can immediately obtain up to $70,000 under extreme circumstances, although exceptions are sometimes granted if you're a special case or particularly well-off.
And then there's also fees if you want to register cctlds, e.g. Internetstiftelsen which manages the .se & .nu TLDs requires 10,000 SEK for applying and then 5,000 SEK per year, along with having to meet certain criteria (regarding it security, data protection, etc.)
> What you will pay to ICANN:
> US$3,500 application fee, which is non-refundable regardless of whether the application is approved, denied, or withdrawn. Following an initial review of completed application materials, ICANN will contact applicant with instructions on how to submit payment.
> US$4,000 yearly accreditation fee due upon approval and each year thereafter.
https://www.icann.org/resources/pages/financials-55-2012-02-...
They also require you to prove that you can immediately obtain up to $70,000 under extreme circumstances, although exceptions are sometimes granted if you're a special case or particularly well-off.