The Frequent Transit Development Option already did this, and more. You can build 21 DUA in R-4 now!
No, there was a housing demand shock in between, so prices charged by an old build OR a new build in 2020 and in 2022 would necessarily be different.
Costs don’t set prices, but prices are related to costs: at different prices, different-cost products can be brought to market. Once prices escalate to a certain level, it makes sense to bring in a lower-cost product. There’s not going to be any demand for $1400/mo microunits in Rocky Mount, where brand-new 3BR houses rent for $1400/mo - but there is demand in downtown Durham, where brand-new 3BR houses are $3000/mo.
Housing prices are set by agreement between sellers/landlords and buyers/renters. If there isn’t anyone willing to pay an asking price, the asking price will fall. But there’s no sense in blaming just developers and landlords for housing prices - not when homeowners, homebuyers, and renters are all also setting housing prices.