It is my personal belief that one week between cold emails is a good frequency or cadence with not sending too frequently or too slowly. Here is a webinar recording on cold emailing that you might find helpful.
What does cost mean to these businesses? The expense associated with implementing a system that provides business with final consumer information goes beyond the money spent on hiring a professional business by belkins.io . It also involves the money spent on software, monitoring, and any changes that might be required as a result of implementing the new technology. These systems can be expensive, but businesses have to weigh the cost of implementing a new system against the return on investment they can get from the system.