The fact is that builder prices can be inflated for a variety of reasons - rate buydowns, ridiculous lot premiums, a "free" upgrade package, a concession and so on. If all the prices have one of those elements present but the prices are similar, how are you going to separate any of it out? See if prices were impacted vs prices of new build sales that sold without using the builder's preferred lender. Usually, the sales office can answer the question, or if it was a cash sale.
The acid test for comparison is that appraisers should analyse the resale market and use resale comps, sales, and listings, not just new builder sales. Some appraisers drop one resale in as a token because it was required instead of including more than one and analyzing. When the resales support the market value opinion, it makes it a much stronger appraisal. If the resales don't support it, then the appraiser has a decision to make -
Builder prices are their own world since the sale contract can include numerous pages of change orders or line item upgrades like carpet level, insulation, door handles, etc. rung up cash register style to arrive at a total. Which we know is not how prices are negotiated on the open market sales.
Then factor in that in a strong market, the builder will announce. "Phase 2 has just opened with a 5% price increase." Well, did the market jump up five % overnight? No. Or the opposite - a builder is ready to close out and sells the remaining models cheap.