Because BYD often charges twice the price for export markets. Sometimes more. Even if a lot of that is tariffs, it still helps fatten the profit margin. And guess what, European customers have noticed they are getting fleeced. So BYD is likely upping their international version so they can say "but you are getting a better model so the 2X price is worth it".
This is the paradox of the ruthless efficiency of the Chinese domestic market; there are simply no significant margins. It's a race to the bottom. The major profits lies overseas, and given the slow progress among Western OEMs, I suspect the Chinese carmakers will retain this advantage for years to come. Other Chinese OEMs are looking at this strategy too. Xpeng has already come out saying they are aiming for more than 50% of their total sales to be aimed at overseas.
