Is there any way to charge per quantity for shipping?

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I sell furniture where each item has a set shipping fee and in large quantity orders, each item is still shipped in a different box that would cost the same as each individual box's price.

1x Chair costs $10 to ship

2x Chair costs $20 to ship

and so on.

How do I get shopify to calculate this? Adding separate weights doesnt make sense since each item has 6 shipping options as is and I cant sit and work out 20x cost options per my 30 pieces of furniture...