We need to find a way to ship Media Mail and non-Media Mail items together without doubling the shipping rates presented to the customer when both item types are present in their cart. When the items combine, Media Mail should be disabled and the items calculated as one shipment for the remaining available rates (e.g. USPS Ground Advantage, USPS Priority).
There is a thread in the Shopify Scripts discussion that addresses our issue, but I am need a different solution. The accepted solution in that thread incorporating a cart script won’t work for us as we are on the standard Shopify plan and couldn’t begin to afford Shopify Plus.
Setting up a separate shipping profile for non-media-mail items also is not an acceptable solution as it ends up doubling the shipping rate by adding together the individual shipping rates for both media mail and non-media-mail items rather than combining them for a single shipment at a lower rate. For example, take one media mail item and one non-media-mail item, each part of a different shipping profile. When combined in a cart, Shopify excludes the media mail rate for the qualifying item, calculates separate shipping costs for each item at the higher rate (say Priority), and then adds those rates together rather than calculating a single Priority rate for the combined items. The overall rate is essentially doubled compare to what it would be if media mail was not an option in the first place and both items were shipped as Priority under the same shipping profile. Sounds complicated, buy if you have tried to work this out yourself, you know what I mean.
We use Shopify Shipping and would be willing to switch to another shipping service if it solved the problem but I can find no shipping apps that seem to address this. The problem appears to be structural and hackable/scriptable only at the Shopify Plus plan. Has anyone found a better solution?