There have always been dealers who will try to undercut the price at which another dealer sells a like-item. Recently, there appears to be more of this activity than in the past, especially in coins certified to be a condition that is relatively available.
The potential problem as always is the eye appeal of individual coins and what value the buyer puts on a coin without comparing it to the second example. Prices are soft in this market sector, especially in late 19th and early 20th-century silver denominations. These are not coins selling near their bullion value.
Bullion-impacted circulation strike and American Eagle bullion coins continue to climb in parallel with their still increasing intrinsic value. This sector of the market is where many investors are active, although there are signs some of these investors are taking a more active role in the scarce to rare area as well. Hobbyists hope that some of the investors dipping their toe into the scarce to rare sector will be bitten by the collector bug and remain long after the market for gold and silver bullion has calmed down.
Minor denomination coins remain as the realm of the specialist, relatively free of speculators. Here the best of the best sell briskly, but otherwise just as with the late 19th and early 20th-century silver denominations there is market weakness. Non-circulating legal tender made for collector coins (commemoratives) continue to do well at their initial offerings, but many times stagnate or decline in value in the secondary market.