Iirc, the helmet was ~$250.
If I had to show my vax card to get into work or shopping then I would, but it may be a little different here in the US. We dont have any digital records or app for our phone, so I would have to bust out this silly looking thing:
As you will notice, its a simple piece of paper that the pharmacist simply handwrites you name, birth date, dose type and shot date. I could literally make this right now on my printer. So basically, I dont have any faith that a person cant fake one easily.