While 3 mana is generally the top end of what you want to spend on a tutor effect, access to mana ramp, combo pieces, utility effects, and more often makes this cost seem like a bargain
Even though it appears on some cards with other permanent types, it's never a creature type, a land type, or anything but an artifact type
I may be somewhat biassed my cEDH deck is a Yoshimaru, Ever Faithful + Jeska, Thrice Reborn deck that also cares about legendaries but I do feel that at the very least even if you do decide to work on another theme for this deck the legend count can always be improved
If you are dropping a small army of creatures into play these cards are a must
From stunning alternate art rares to competitive favorites, these cards are dominating both collector markets and online auctions