It all depends on how often cables need replacing. In practice, it's extremely
uncommon for us to ever replace a cable. After a server is installed in a rack, it rarely gets moved (VLANs, provisioning, networking, etc. are all handled by our automated platform, so the physical location doesn't have to be changed). Because the servers aren't moved, the cabled don't get moved, and without any environmental changes, the cables rarely (if ever) go bad.
Not sure of the statistics around how many cables get replaced in a single facility in a given year, but our overall zip-tie cost is considerably less expensive than Velcro would be.