If it can be shipped safely with the appropriate amount of bubble wrap and peanuts, then I don't see a problem fitting them in a smaller box. If someone just throws parts in without any protection yeah I would have a problem with that for sure.
Greed? That's reserved for sellers who advertise a shipping price and don't refund the differences when actual cost is lower than expected. By show of hands how many here have done that?
The way I see it sellers can either bet on the 5% chance something goes wrong or the 95% chance everything goes smooth. And when that 5% does come around, appropriate return policies are in place and negative feedback can be left if necessary.
Back to the point though, sellers need to figure out the best way to ship items to their customers. I choose flat rate priority mail because it eliminates shipping "quotes", it arrives quickly (even internationally) is insurable/buyers protection safe, and lastly I can jump on eBay and list an item without thinking about the weight/cost and avoid the crazy buyers slingerland ran into. It leaves very little liability on my end when all these components work together.
***And also I made a huge mistake...lol I shipped 10 Streamline Lugs, Complete Radio King Tom mount and some long tension rods in a flat rate box. Much more possible than lg beavertail lol sorry all. my bad DOH But that's still a significant amount of hardware in a small box.