The phasing plan is the first thing a planner will look at, and most subdivision ordinances have language written specifically to stop it. Look for a section on successive or serial divisions, sometimes titled circumvention, that counts divisions of the parent tract cumulatively regardless of timing or intervening ownership. Where that language exists, lots 6 through 14 pull the whole tract into major review and the paving condition applies retroactively to the road serving lots 1 through 5. Some counties instead require any minor subdivision to include a note on the plat reserving future right of way to county standard, which achieves the same thing more gently. That single ordinance section decides whether your plan exists, so read it before you pay for another drawing.
Your $45,000 comp is doing more work than the road number. Those comps almost certainly sit on existing public roads. Lots on a private gravel road with a maintenance agreement typically trade at a discount, and the reason is financing. Plenty of lenders won't write a construction or lot loan without a recorded maintenance agreement and sometimes a paved or all-weather access finding, which thins your buyer pool to cash and local banks. If the private road version of your lot is a $37,000 lot rather than a $45,000 lot, 14 lots at gravel is $518,000, and the gravel road at $55 a foot is $165,000. That's a different deal than the one in your post, and it's still probably a better one than paving.
Two other costs I'd force into the model now. County improvement guarantees, meaning a bond or letter of credit for the road until final acceptance, tie up real money for a year or more. And 14 soil tests at rural county rates plus reserve areas will find at least one lot that doesn't perc, which is how a 14 lot plan becomes a 12 lot plan after you've already paid for the road serving all 14.
