kit plane pricing confusing

Ok, I am confused. Take Lancair website for example.Propjet kit, price
115k. Ok. Click on engines and props.Engine 120k, prop 18k. Ok.Parts
and Options.Huh? what parts do I need and which ones are options?I
would say that cabin heat at 20,000 ft is a necessity, not an
option.Somewhat confused.Next-- firewall forward items. Are these
parts or options?And what is a kit anyway, if one has to get all kinds
of additional stuff that is necessary, not just an upgrade? Maybe I
should buy their info package that may shed some light on the subject.
What do you folks think?