Options and upgrades are a huge profit center for these builders. Huge, as in 300%-of-cost huge.
As for not knowing? Don’t kid yourself – they know exactly what they’re putting in and exactly what they’re charging you for it. The reason they’re not showing you the detailed breakdown is because they don’t want you to look at what they’re charging you. People are prone to price shop when they can make their comparisons.
Stick around – I’ll bet at some point you’ll be able to buy a shell with no flooring, fixtures or appliances and design your custom interior yourself. The only question for the builder will be how to avoid disclosing that sale price in the public records so as to not piss off their other buyers.