Compared to its cousin Charisma, this card doesn't really see much love, despite serving an essentially identical function. With that said, you should watch this space because as more and more must-have accessories are released, this card will only increase in value. I'm willing to bet that a year from now (or even sooner), we will start seeing this card being considered a lot more.
As things currently stand however, there just aren't enough high-powered Accessory cards to merit purchasing Relic Hunter for pretty much every investigator.
The one massive exception is Zoey Samaras. Her signature card, Zoey's Cross is an absolute must-play when you draw it. It's so powerful that you'll probably think twice before purchasing any other accessory cards, as they'll essentially just be used for their icons if the cross hits the table first. This is a huge shame, as not only would Zoey really like to pick up an Elder Sign Amulet at some point, but she is also the only investigator who has access to both Holy Rosary and Police Badge, arguably the two strongest accessories in the game right now.
But with Relic Hunter, Zoey can fill her deck with these accessory cards and get good use out of all of them. If Zoey's Cross is the card you never want to leave your side (e.g., the accessory equivalent of Leo De Luca, Dr. Milan Christopher), the others are all expendable and can be replaced once they've served their purpose (Art Student, Guard Dog, etc..)