Combined for sale listing?

Dana67Dart said
But at 10 items per ad, that would eliminate the problem very fast.

And create other problems...

Dana67Dart said
Selling things in a garage sale fashion is a better and more efficient way to sell parts regardless of the type.
If you list 100 items you push 90 of your posts and all of everyone else's posts off the home page.

Actually, it can be and often is, pure confusion. I know, it looks good on paper, but there are a number of reasons the rule is there.

It's hard to classify such an ad as mechanical, body, etc, making it harder to find.
The ad always needs to be updated to reflect items sold, which often doesn't get done.
There are many more questions per thread due to the number of items, creating much longer threads and making it much harder for us to moderate.

...to just name a few of the reasons for the single part ad rule.

Dana67Dart said
ALSO.... I think that the paying members should have a say on the rules of the site.

This rule has been in place for over 18 years.