Not to give any credence to the claims in the letter, but selling in other countries involves labeling requirements unique to that jurisdiction (for example, French/English language labels in Canada) which would necessitate separate smaller runs for at least some of the production.
While the production runs for the raw materials are larger, the lots for bottling/labeling are smaller, and an added expense.
Edit: In addition each country has their own laws for packaging, handling, sales and shipping of dangerous goods, which may or may not apply...
Once again, not at all trying to prove any claims, just making a statement that manufacturing is not a monolith of more=easier.
Also I imagine most of your frustration on this subject stems from Facebook? Came in here all guns blazing! 
If that's what they'd said...i.e,. "We're restricting production and sales to our US and Canadian markets going forward due to excessive costs of producing for overseas markets" I'd buy it. But that's not what this letter says. It says in the same breath that Testor's is
ending altogether and yet only overseas shipping will be impacted. It still smells like crap to me.
Maybe they do plan to stop shipping overseas. Dunno. But the claim that Testors is closing is crap, so I would not put any stock in any other claim in the letter until independently verified.
My frustration with people not fact checking extends
waaaaaaaaaay beyond Facebook. And I'm not mad at anyone here. I'm annoyed at the initial group of folks that spread this around like wildfire, giving it legs long before it got to the Railwire. I'm worried that some of these hobby shops will make decisions going forward based on this nonsense and that would have a real impact, not an imaginary one.
