If they are problem free, the $10/coin is fine. You'll never find problem-free silver Ike proofs for less. The ones that you pictured, I personally wouldn't touch at $10. But if the price can be negotiated to $8/coin, then that would be fine. Also, you need to be aware of the different varieties of the Ike series as it is prime for cherry-picking since so many don't have the knowledge including most dealers. For example, the Crater Snake variety that I mentioned in only a PR66 grade, which is a rather low grade for modern proofs, is a $100 coin. By the way for the '71-S, there are 8 different recognized varieties.