At some point they introduced a new ‘V2’ pricing plan, probably to compete with the overall drop in the market prices. They now have much cheaper plans compared to V1, for example 10GB went from 5,980 to 3,280 and 30GB went from 12,980 to 4,380. V2 also supports tethering which V1 didn’t. The only catch is you have to get a new SIM and number.
P.S. Yes, I know there are cheaper plans available from Japanese carriers, this post is just for Mobal customers who may not know there’s \~60% savings to be made.