Along the lines of the post I just added to the other thread, I don't think the dollar amount matters. It's more what is done/added to the boat.
Unless it's a significant change to the original structure/build of the boat, I'd still call a very, very expensively equipped Hunter/Catalina/Bene/etc. (especially one like Sequitur) an off-the-shelf production boat (maybe minus the cutter rig mod).
All mass production boats permits some customization further than the optional that they purpose. Many times that customization works between the factory and the dealer. Of course it is important to have a major dealer and a knowledgeable one.
Some years ago I considered substitute my Bavaria by another one a bigger boat and I was thinking in the possibility of having a cutter rig: No problem said the dealer, we ask the factory to do the needed reinforcements and we do the rest. So, if I had bought that Bavaria would it not be a production boat? ….and Bavaria is really a mass production boat.
More recently I was very close to buy a Salona and they were available to do lots of alterations on the boat, including a new and heavier keel, a bowsprit and even a special system to carry the dinghy on the transom. If I had that boat it would not be a production boat?
Regarding price and optional equipment brands like Bavaria have a huge list of optional that can really make a different boat and I am not talking about a teak deck or the interior TV but about a complete safety system with holding points and integrated jacklines, lead keel, offshore sails , performance rig , radar, outside plotter and so on. Just to give you an idea my previous boat cost me 50% more than the standard boat. Of course, it was as mass produced as any other Bavaria, just better equipped than most.