If you are inquiring about modern silver US commemorative coins (1982-present), then "Yes" the market price for many of them is tied to the current spot price for silver. A number of them do command a numismatic premium, but you can likely buy half (or more) of the modern issues for little more than their melt value. I was at a coin show this weekend and saw a dealer selling more than a dozen different designs of the modern silver dollar series for $23 each (capsules only, no box/COA).
The selling price of the coins of the classic US series (1892-1954) are not linked to the current spot price of silver - they all carry a numismatic value in which the intrinsic silver bullion value is a very minor component.
Regarding whether to purchase bullion or modern commemorative coins, remember that the commemorative silver dollars have about 0.77 troy ounces of silver - they are not a full ounce.
Whether silver is at $20 or $30 per ounce, the selling price of bullion coins vs. many of the silver dollar commemorative coins is going to be based on melt value. So, the price point of silver, relatively speaking, does not matter much when comparing the two.
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