The 1857-O Dime has the exact same mintage as the 1858-P, and the two coins "behave" almost identically in the PCGS Population Report. This is quite unlike the earlier Dimes from the New Orleans Mint, many of which have relatively high mintages but few survivors.
The 1857-O Dime is plentiful in all grades up to, and including, MS63 and MS64. Even Gem example can be found with relative ease. MS66 examples are scarce to rare and anything better is a true prize. None are known better than MS67. Surprisingly, none of the PCGS MS67 examples have ever sold at auction, to our knowledge. They would most surely exceed the price record of $9,350 for a PCGS MS66.