here's all i know. when i built my defender 110 a few years ago, i added all sorts of accessories, including roof rack, ladder, undershield, etc. the configurator and order sheet definitely had the appropriate asterisks saying "excludes installation charges." but when my truck arrived, i went to pick it up, and all the accessories were already installed at either the port or the dealership, and they never tried to collect a single dollar for installation. i've had the same experience with other cars and trucks i've purchased from many different brands. never once, have i been charged to install something that was part of an original build sheet. ineos and their dealers certainly have every right to do this, but in my opinion it's just bad form and comes off as a "low rent." no issue paying to have accessories installed (or doing it myself) if they were ordered after the fact. have done that plenty of times.
the smarter move is to just factor those costs into the overall price and let the manufacturer and dealer sort it out behind the scenes. i'd rather have my customers leaving feeling like they got more, not less, than they were expecting. each and every interaction like this is an opportunity to build long-term brand loyalty. and IMHO that's definitely worth a lot more than a small cash grab by the dealer.