I know why Tamron are so hot on grey imports, they don't have subsidiaries in other countries, they use independent importers, well they do in the UK, where Tamron is represented by Intro2020, who also import Tokina, Cokin, Slik, Metz and many other brands to the UK and Ireland. They bear all the costs of supporting the brands, both pre and post sale. Even where the wholesaler of a product in a geographical region or country is a subsidiary of the manufacturer they are usually incorporated in the country that they operate in. Again they are responsible for dealing with all of the pre and post sales support costs.
If you are running a business selling products that you spent a good deal of money on advertising in the many different types of media we now have. Alongside of which you have a workshop to provide post sales support and service, how would you feel if you found that a noticeable proportion of the products that you are receiving were not actually sold by you? Would you want to have to pay for this out of YOUR pocket? If the manufacturer subsidiary companies have any local shareholders, then the same applies to those local shareholders, why should their company support products that they did not sell?
I find it the same as going into any specialist retailer, asking for lots of presale advice, which the retailer will give in the hope of making a sale, then going and buying the product for the cheapest possible price online. As if that is not bad enough when they have done that, and have some issue with the product, they go back to that same small independant retailer for post sales advice. I have been involved in specialist retail for about 15 years now, and I have seen this happen almost weekly. Because of the nature of the products, which pretty much cannot be shipped by private individuals here in the UK, people will expect the retailer they did not buy the product from to organise a return to the manufacturer for them, simply because you sell the same product. What is even worse is the manufacturers who tell owners of the product to do this. It generally takes about an hour of time to process a product return for repair, which in most cases would wipe out any profit made from selling the product in the first place. So doing it for a product you didn't sell is a double whammy, it's costing you money, and your competitor is still keeping his full profits from the sale.
Alan