My lien servicer earned more than I did on a 14-certificate block and I think that was actually fine

The ratio that jumps out is 3,100 on 60k deployed, which is roughly 5% of capital consumed by servicing against a gross return that, working backwards from your 6,400 net, looks like something in the 15 to 16% range before fees over 19 months. At that scale the fee load is punishing. At 600k with a similar certificate mix, a servicer does not charge 10x the fees to send 10x the notices, and that's where the unit economics actually shift.

The assumption doing the most work in your analysis is that the title catch was exceptional rather than routine. If your servicer's due-diligence process surfaces defects as a standard part of their workflow, you priced a systematic benefit as a one-time event. That changes how you should think about the servicer relationship at scale: it becomes less about administrative throughput and more about underwriting partnership, and that distinction matters when you're negotiating fee structures.

The risk you did not name is jurisdiction concentration. One county means one set of redemption rules, one foreclosure timeline, and one bidding pool. The servicer's value to you partly came from their familiarity with that county's specific procedural requirements. If you scale into multiple counties to find better auction competition dynamics, the servicer relationship either needs to cover that geography or you're back to managing compliance fragility yourself in each new market.

Confirm with your servicer in writing how their fee schedule actually changes as volume grows. Some structures use a flat per-certificate fee that scales linearly, some use tiered minimums that compress at volume, and those are very different conversations at 600k.

What does your servicer's fee schedule look like at the next band up, and is it certificate-based or capital-based?