Based on v1 satellite cost estimates, under $5MM for 20. It was v3 sats, don't know the cost on those yet.
Around 20 minutes into the flight, they deploy 20x v3 sats. Google search tells me those cost more than 1M USD each. Yikes... they burned up 20M USD for a "few tests". Damn, space is expensive! The official video says that SpaceX only had twenty minutes to test the deployed sats before they fall back to the atmosphere.