I always find this topic interesting. Personally, I have said it before in other capacities (lighting especially), but list doesn't exist if RB, HUNTER, TORO, and all the other so called commercial grade manufacturers don't have some rules. I don't knock you for shopping through irrigation direct or sprinkler warehouse, but the fact that you don't have to have any formal licensing or tax id to purchase there at wholesale is something I blame all the manufacturers for. WTF is list, if anybody can buy it at wholesale with one simple internet search? It's a figment of the imagination. That's my rant on that topic, as for markup on parts I play by the rule, the more expensive the item, the higher the % of markup. Im not going to pay $200.00 for a controller and only mark it up to $260.00, then install it in 1 hour and and collectively charge $360.00 for labor and materials. I generally find the more expensive the part, the more knowledge needed to install (not always, but generally) and the more effort it's going to take me to replace it if a warranty issue occurs. Im not going to mark up nozzles and fittings 500% because generally it's brain dead stuff that isn't going to make me much. The labor on those quick ticket items is generally worth it cutting my markup.