Tikis had been on sale forever in Shrunken Ned's for like 50-100 credits. A week or so ago they were quietly removed from Ned's. So they are not rare, but they are not for sale. Pink Tikis were "beta" and are very rare, but have been given out in staff games on occasion.
Yellow, Cyan, and Red tikis are not considered rare yet, but they are in demand now, so you could probably get something nice for them. Pink tikis are SUPER rare. You could get Inferno for one of those!