Price is always completely OTT on their system, it drops down to something sensible when a discounting code is entered... you get a better code the more you buy... DIYers get one generic code, big contractors will have a specific code for themselves
In theory, in practice it's quite hit and miss, I've had invoices on which the discount has been "forgotten", right up to the 98% on cable.
Plus, they make it up on the spot often as not depending if they like you and how their days going. If I get an apprentice she'll be blond with big breasts.