It isn't that cheap if you have to consider different branding and marketing campaigns when you want to expand to neighbor regions. The cost of covering the EU market can increase really fast.
Edit: it's also an ongoing cost, so the earliest you start to support additional locales the more expensive your general product development becomes. Once start to translate your UI you now have to keep it up-to-date all the time. The more translations you have the more expensive that process is when developing new features, both in actual time/energy to be sure that your UI/UX work well in your supported locales, and expenses for translators.
Edit: it's also an ongoing cost, so the earliest you start to support additional locales the more expensive your general product development becomes. Once start to translate your UI you now have to keep it up-to-date all the time. The more translations you have the more expensive that process is when developing new features, both in actual time/energy to be sure that your UI/UX work well in your supported locales, and expenses for translators.