Sold lot 4 of 6 last Tuesday and the check was $11,400 more than I modeled

Lot 4 buyer probably had a specific build plan that needed that footprint, not a market signal.

Did the corner lot have road frontage on two sides, or was it just a better interior position?

The engineering number is one I would push back on a little. $34k for a 6-lot split in Hays County feels like you got a good run. I have been watching similar splits in Williamson and Caldwell and the platting alone has been coming in closer to $42-48k when you factor in the second round of county comments, which almost everybody gets. So your cost basis might actually be tighter than the average person attempting this right now, which changes how conservatively you need to price the back lots just to protect margin.

The $57k comp from two miles north in 2023 is also doing a lot of work in your model and that is where I think the real issue is. Hays County absorption has moved fast enough in the last 18 months that a 2023 sale is almost a different market, especially sub-$75k raw land where the entry buyer pool has grown. The $72k on lot 4 might not be a one-off at all. I would sit on the back two for another 30-45 days before repricing down, because dropping to $54k now after a $72k close in the same plat is information you are giving every buyer who pulls the recorded sale. They will use it.