And to do the research/security checks, maintain the database etc etc. It doesn't just start and stop with you hand them details and they fire them into a computer which prints out a card.
At university registration it takes 60 seconds for someone to take your photo, verify your details and print your card. Assuming they are paid minimum wage that's 9.3p per card. In any case it does not cost £50 for what is a minimal amount of work. It's the same with birth certificates, complete rip off.