We once shipped a catalog page we were genuinely proud of: clean grid, tight product cards, everything lining up. Then we ran it through our translation pipeline for a second market. It came apart. Names that fit one line in English wrapped onto three, cards grew to different heights, and on phones the price and the buy button slid below the first screen.
Nothing was broken in any way a test would catch. The page looked fine in our language and quietly stopped doing its job in the other one, until someone noticed and told us.
What it cost was mostly trust. We had told the client the page was finished, and it was finished in exactly one language.
So now we design to the longest text we can realistically expect, not the shortest, and we look at every layout in the target language before anyone calls it done. If you sell in more than one language, it's probably worth opening your own storefront in the other one today.