- Customers always prefer flat rates, they don’t like surprises, they will always prefer someone with flat rates as they save some time rather than waiting for an unknown price.
- All my rates are flat assuming the package will never exceed 500g (claealy mentioned in the shipping option description), this includes packaging weight and cost. If a specific order exceeds the rate the customer has selected, I can always add extra shipping costs during order review based on estimated weight (from my slicer) or change to a more convenient shipping option (if the printed object exceeds the package size required by the shipping service/carrier)
If you need to change the shipping option at some point, do it during order review, otherwise it’s too late and there’s a risk that customers will reject the proposal after printing the order.
3DHubs are not supposed to take 12.5% from the shipping costs so no need to add that to your costs.
Like ejalal said - my customers seem to like flat rates, with no surprises.
Even when a quoted shipping rate came in way too high (e.g. for a tiny part that can be shipped like a letter) most understand that this is not an ecommerce store or a bulk shipping service - shipping is almost part of the part cost, so going over on shipping has never bothered them. I often offer a manual postage discount on their next order to entice a future order.
Just spell it all out in your description and offer flat rates, and spell out that you are flexible too. 3D Printing is a manual and flexible technology, and 3D Hubs is a manual and flexible service too.
Unsure on US postal, but here in the UK we can get standard Royal Mail (translate - USPS) tariffs for package size and weight. In the UK it boils down to a couple of sizes and a couple of weights, so I can offer a couple of simple known services, one being next day delivered. Best look up what your local shipping firm can offer, and offer those to your customers as is.