&gt;I suspect (because I have a similar challenge in our own ecommerce system) that the model underlying the representation of products has at least one additional layer of specificity, that&#x27;s not directly revealed to the user. Consider that you&#x27;re looking at Products, but what they&#x27;re really manipulating are products as sourced from a particular supplier.<p>There&#x27;s no doubt that&#x27;s the case, but it also isn&#x27;t that big a problem to solve (at least for amazon, your mileage may vary, possibly my commiserations depending on how good&#x2F;bad your system is to work on).<p>I know this because of the &quot;Does amazon ship to...?&quot; plugin, which can iterate over every seller instance of a specific item and return it&#x27;s eligibility for shipping to your country, along with an independent shipping price and item price. It can process two dozen instances in about a second or two via whatever API it uses.<p>Considering this is possible and frankly not all that difficult, I&#x27;m placing the blame for amazon not using a bit of JS-foo to run this form of processing server side (where it will be way faster) and deliver results to my browser asynchronously as they are finished squarely at the feet of amazons marketing department. This has the stink of &quot;if we show it to them anyway, maybe they&#x27;ll buy it and send it via a shipping service&quot; all over it.