I don't think that these protective cards are getting enough love. It is hard to consider for three experience (along with Bulletproof Vest), but I think that these are definitely worth the purchases. I tend to lean towards including Elder Sign Amulet in Roland Banks's deck and "Skids" O'Toole's deck since they have such low sanity values that this can effectively double what you can sustain throughout the adventure.
You have to consider that the slot it is consuming is likely not even used. In my Roland Banks deck there is an absence of accessories. So, when adding this in there is no conflicting option to worry about when you draw it. It is never a dead draw card. Especially with the symbols that it comes with. Cards meant to keep you alive are not typically the fun cards, but they are the ones that get you the additional experience in the long run to survive and make it through the campaign and get the cards you really do want later.