"This offer is only available to new users of 1Password."
EDIT: Someone answered already
I'm wondering if I can just create a new vault and transfer
You probably could. I'm on a family plan so it's a little more complicated because it's not just my vault I'd have to consider. Still, 1Password is a sufficiently good platform to me that I'm okay just continuing to pay the subscription price. I pay once a year, so it's not like it's a monthly burden for me.