One of the ways we're going to beat this system is by finding people with larger yet untapped audiences.

If you have 1 million followers you are probably approached for shoutouts several times per day. If you have 100,000 followers you are probably approached several times a week (and more if you're on a shoutout selling network). If you're approached that often, you can piece together some semblance market-based pricing (using what people are willing to pay), and likely have an idea of what the price of such a service should be.
What the price should be is "expensive." We want to find the people who don't know it should be expensive yet.

In my experience, those with between 50,000 followers and 100,000 followers are virtually never approached for shoutouts. Because of this, they have no price set for a shoutout, and we can often buy shoutouts from those folks for cheap.

Buying a shoutout from an account with 1 million followers has run people I've worked with as much as $20,000. Yet I've purchased dozens of shoutouts from accounts with ~50,000 followers for $5-10.
Let's assume, for a moment, we put in the legwork to find 20 accounts with 50,000 followers and paid each of them $10 for a shoutout. We pay $200 to reach the same number of followers other folks are paying $20,000 to reach. A $19,800 savings by putting in a little more work and creativity - that's exactly what growth hacking is.
Your numbers may be slightly different, but $10 per shoutout serves as a good starting point.