I don't know if the sellers got the wrong price but at £3, they seem very cheap to me. Just bought two sets. The seller makes a bit on post, £1.20 for the first plug, then 50p for the rest - but still cheap.

Item number is 130281015736

They're CR8EH-9 suitable for the CB-1, not sure about the SF.

they certainly fit my sf, tyvm i got 2 sets too :D