[twelve40]

> It's a very great deal of money, so there should be some really good reason

They were probably outright selling lots of currency during the hot days in Feb and March to stop the immediate exchange rate freefall, that's where the $50B most likely went. Since then, the imports plummeted but the export dollar amounts soared because of high energy prices (despite slightly lower physical volumes), so the curbs and the market took over for now. We'll see what happens next.

Btw: no, selling rubles is not forbidden, as a consumer you could sell rubles pretty close to official exchange rate in April (not sure about now), and they just announced you can wire $50k to foreign banks per month starting today. No idea about larger amounts.