Oh, how much for this guaranteed pull? $50?

One time 5000 yen deal. I hear last Christmas it was free (again, one-time). They don't exactly want to give you these 'choose your waifu' moments often.

Now, last month there was a "get a 6* you haven't got" deal for 5000 yen which wasn't limited to one roll. There was a cut-off point so the newest 6* weren't available from that.