WG started seling bonds for money. As much as I remember (not sure) they told us we’ll never be able to buy bonds for cash? 

This is an offer from NA server (Rykoszet is not 100% exact on this) but we’ll probably see it on EU too. 

UPDATE: This is the source: https://www.reddit.com/r/WorldofTanks/comments/a37dkm/bonds_as_a_gift_for_premium_time_bought/