The rule that survives every market: buy what is hard to change later, and add what is easy yourself.
Upgrade the things that are structural, buried, or disruptive to change afterwards. Do not upgrade the things you could replace on a Saturday.
A builder's margin on finishing upgrades is generally healthy, and the same item frequently costs less installed afterwards by a trade you choose. The exceptions are the items that cannot practically be done later.
The pattern we see on resale: the buyer who spent on the lot and the structure recovers it. The buyer who spent the same money on finishes rarely does — the next buyer simply expects a nice kitchen at that price.
Usually more negotiable on incentives than on headline price. Builders protect list price because it sets the comparable for every remaining home in the phase — dropping it devalues their own inventory. So they would rather give you upgrades, cover closing costs, include appliances or landscaping, or throw in the basement development.
That is genuinely worth having, and it is worth asking for. Just be aware you are usually negotiating value rather than price, and that incentives are easier to obtain late in a phase than early.