Stative or progressive

[mino]

Dear Learner

Would you look at these and tell me the different meaning of them

-a\ Are you happy with the school you decided to send your daughter to?
 b\Yes, indeed. But it pretty expensive. It..COSTS/IS COSTING usan arm an leg to her there, but we think it's worth it. It won't last forever.

progressive is also correct, but what dos it mean?

waiting for your reply

mino
just humble