I don't know if this is a recent policy change, but it is not the complete amount but only 50% of the remaining annual amount as per their website[1].
If it were something involving physical goods or services I can understand, but 50% penalty is still a crazy amount for a hosted software service.
The billing your credit card 50% is a "well we tried" type thing. They're happy if it works out, but not unhappy if it doesn't.
It was an error on their part so take that as you will, but... scary letter != inability to borrow money.
(And just for the record, I no longer subscribe to that rag.)
A rather famous example of this is when Columbia House sold off accounts from their scammy operation to a debt collection agency, with many folks unaware that the company claimed they owed money.