I already have one waiting to be finished.
Some replicas are cheaper than others, for various reasons. Some kits do not come with liners in the body shell, some kits use epoxy resin instead of vinylester, some kits body shell are paper thin while others are up to 1/2" thick, and so on.
Completed kits prices can range from $25,000.00 to $100,000.00. It all depends on what you expect from the car.
Anyone looking to buy a completed kit needs to do their homework. Sometimes a title cannot be transferred from one state to another, is there a parts list, assembly manual, is the manufacturer still in business, who built the drivetraiin, is it still in warranty, what custom options have been applied, what is the paint color and so on.