Avery has high system test costs, because his project spends more time looking for defects than fixing defects However, Avery's total defect fix cost for Avery's larger project is lower than Dan's smaller project. And Avery's post-release fix cost is substantially lower.
Each project will have its own cost to fix a defect, because the cost depends on the activities undertaken in the project and when you start tracking defects, as well as cost to fix. Use your fix cost to decide how you want to proceed with this project or the next one. If your cost is too high, and you're not yet in system test, you could try some defect detection and prevention techniques. Just make sure that if everyone is associated with finding and fixing defects that you don't only count the fix time, that you count the detection time also.
If your find-and-fix cost is high in system test, what's the risk of releasing early? Avery might have used his find-and-fix cost of $3333 to chose to end system test early and release early, knowing that his post-release cost would rise. Only Avery and his management could estimate the risk of releasing early.
Use the pre-release fix costs to see if you and your staff are being cost-effective in your pre-release activities. I've found that each organization has a typical post-release cost, not necessarily tied to the project. So I use the post-release cost to help define release criteria. This helps you manage the risk of too many defects to fix after the release.
Knowing how much it costs you to find and fix a defect allows you to ask questions about how you're finding, fixing, and verifying defects. Yet another way to build a system with the appropriate quality.