The cost gap on a $20,000 balance
Carrying $20,000 for a year costs roughly $1,100 more on a card than on a line of credit.
On a line of credit at 12% APR, $20,000 repaid over 12 months runs about $1,777 a month, roughly $1,324 in total interest, and about $21,324 all in.
On a credit card at 22% APR, the same $20,000 over the same 12 months runs about $1,870 a month, roughly $2,440 in interest, and about $22,440 all in.
That is a difference of about $1,116 on a single $20,000 balance. Scale it to $100,000 and the gap becomes the difference between a good quarter and a flat one. And it vanishes completely if you pay the card in full, which is the entire argument for using each product for the job it is built for.
