For your use case, prioritize history over price, full stop. Ask for the range’s previous use, check it across the major blocklists and mail reputation services yourself rather than taking anyone’s word, and look at whether it has been sitting unannounced for years, which is often cleaner than recently active space. Region matters too, since some geolocation databases handle certain ranges better than others and that affects your customers directly. We went to Buy IPv4 addresses safely , with IPv4.online and specifically paid more for cleaner blocks. Honest note: geolocation records lag for months after a transfer, so plan for that regardless of who you buy from.