Are you allowed to sell craftable items on the cargo shuttle in mass quantities for a profit?

This is also know as, “money printing.” It’s where you craft steel into things like Gas Scrubbers, Gas Vents, or Racks. These items sell for $100, $100, and $150 respectively. If you use the entire inventory of steel sheets in a steel-sheet crate (90 sheets) you can get up to $9,000 from crafting. With the $1,000 cost of the crate, you get a net profit of $8,000 for selling Gas scrubbers, and $12,500 for racks. You can cut out the cost of money printing by deconstructing chairs and tables throughout the station. There are several other crafting menu items that work like this.

Would “money printing” be considered using an exploit which breaks rule #7?

It is not considered an exploit for the purposes of rule enforcement, but admins can choose to respond to it by interfering in the round to negate or counter the effects of it. Responses like editing the cargo budget or bombing cargo are not uncommon.