like i said it all depends on what options you order with it as to what the final cost is going to be. give bill a call and talk it over with him and see what direction you want to go. his kit is just that. a full kit that you can drive into the garage with your stock suspension and a couple days later drive out of the garage all complete and you only need to supply brake fluid and bearing grease.
i would deal right with bill and RMS. he builds the thing and can and will answer any questions you may have. that mopar site selling it you may get some clown that barley knows what it is and won't be able to answer any questions about it... i would also talk with bill over trying to spec it out on his site. the site can be a little confusing.