Has anybody ever given any thought to why there is ejector pin marks. To how some models have very little, then others have them everywhere, then once in a great while you can find the one that has them everwhere, with one that has just a few. To why they can one time give a model with very little, then you can have another of the same model with pin marks all over it, have you ever thought why?
I think I have figured out why, but I would like to here other peoples ideas to, that maybe I'm wrong. My idea is they run the machines to fast and the plastic doesn't have time enough to cool, letting the pin stick into it, and when they don't have very many, it is when the line broke down, and it takes a while to get back up to speed, that is why some of them come out with very little pin marks.
The reason I think Tamiya charges more is they won't run their machines at full blast, which make for a lot cleaner casting, and sense they won't run full blast they haft to charge more to be able to pay the wages to their people. Just my thought what do you think?

I agree the speed of the machines has a lot to do, how fast and hard the ejector strikes the piece.
I think it has a lot to do with the quality of the plastic used too. A higher quality plastic may be 'stiffer' and resist the marks.

It is a tooling and quality control issue more than anything else. I fight it everyday here at the foundry. We use ejectors to "kick" shell cores out of cast iron core boxes that are heated the same way injection molding tooling is heated. The pins are adjustable. If they are not flush with the face of the tooling you will get a positive or negative defect on whatever you are molding. The picture below has a core with a positive defect caused by the pin staying below the surface of the box. If they stick out too far you get the round holes we all have to fill. It takes time and attention to makes sure all of the pins are flush. That, and the pins are attached to a separate plate. The plate and the box heat up at different rates and if you don't wait until they are both the same temperature the ejectors don't go where they are supposed to go.

Sorry, you guys it me where I live. Hope this not so brief explanation helps anyone who read this far... LOL

It is a matter of engineering of the kits and the molds. A well enigineered kit, also probably more expensive, will have the ejectors strike either the sprues and/or surfaces that do not show after kit is built. Otherwise you end up with kit parts with numerous marks, often where they show.