They also have a promo code
NFLYDIGITAL2408, which gives a $5 discount on domain registration or transfer. More details about the promo can be found in this NamePros forum thread:
https://www.namepros.com/threads/special-offer-register-or-transfer-your-domain-to-nfly-com-and-get-a-limited-time-discount-of-5.1332459/unread