If the cost is the main issue, there are excellent open-source and free network scanners that do much of the same work, such as:
This write-up explores the legal, security, and functional implications of using cracked or unauthorized license keys, and highlights the safer alternatives available for network scanning. Netscan X License Key Free
Identifying HTTP, FTP, and other services running on network devices. The Risks of "Free License Key" Websites The Ultimate Guide to Netscan X: Unlocking its