I buy PCGS 69's and only bid spot plus $15 (slab cost) and win easily. I think many 70's way overpriced and have no interest in them. For me a 69 is more than good enough to fill the hole.
I would like to meet the fool who paid $4k for a 1oz. bullion coin..MS67-MS99 all worth the same to me.
For Ikes do business strikes and silvers (or at least used to do the silver in the past) but I am not sure about proofs. MS Ikes are really hard to get snickered in the higher grades. I don't know off the top of my head is Photoseal does Lincolns but if they do and you wanted to go for all three I would start with CAC or Photoseal. If you have those two already I wouldn't think QA would disagree.
Photoseal only applies to Flying Eagle and Indian cents, so no treeple-steecker for Lincolns. I asked James about QA + CAC stickers when I wasn't busy taking pictures, wandering the bourse, making plans for evening barbecue, or chatting with the blonde you've all noticed. He said it can happen because there is some overlap between the two services, but also that there's nothing automatic about a coin with one sticker getting the other.