I have a question about discount for ordered car vs car in lot

this is what i understand how a dealership works, but maybe i m wrong

To be a dealership, they have to order certain number of cars to keep their quota and maintain status. I know that manufacturer also give a dealer holdback (cost to keep the car in lot) up to 90 days usually. If you order the car, the dealership is already eating that holdback and also already guaranteed one car off their order quota number, that means less cars on the lot. In my opinion, that should give the buyer at least the same discount as the car on the lot if not more discount than the car on the lot as the dealership already get profits from the dealer holdback.

so why does the car on the lot can command more discount than ordered car? maybe i m missing something here