Per Product Shipping Surcharge lets you define custom shipping surcharges on a product-by-product basis. Surcharges are automatically added on top of your existing flat-rate shipping cost at checkout or you can even override the flat shipping rates to only display and charge what that product shipping cost demands.
This is for a wide range of people but mainly those that are in manufacturing with a wide array of SKU’s and have to have a minimum shipping charge. But every now and then, a bulk item is ordered and you may need to adjust the shipping charges to match the item to be shipped.
There is a lot of flexibility in the plugin: