How much cards is 1 refined metal worth?

It depends on the value of the cards

i find a guy who was asking me to trade my cards each for a scrap so a ref must be at 9 cards i suppose, I dunno if that is the correct price per card

I ref is worth roughly $0.25

Its 8.33 ref for a tf2 key. Keys are about 2.5 USD or so. So a ref is about 30 cents, which is about 3-5 cards.

Normally

1 Scrap = 1 Card

Okay, thanks guys!