Unfortunately I've seen the complete opposite. We've had to purchase dedicated sending IPs for some of our clients that maybe send 50 emails a week.

Why? Because these emails are super important transactional notifications and we constantly saw stuff getting blocked on shared IPs. It would work fine for a while then get RBLd causing major major issues.

Sendgrid, sparkpost etc support all said the only solution was a dedicated IP with them. This does seem to work FWIW, but it's probably working out the same cost per send as sending a physical letter at this point!