Swiss Pass

Tim, I have never heard of the price being reduced. It is a fixed price, CHF 216 for 3 days, more for longer periods. Swiss ticket prices only change every 2-3 years.
Details from SBB website: https://www.sbb.ch/en/leisure-holidays/travel-in-switzerland/international-guests/swiss-travel-pass.html

Foreign resellers may have higher prices, and their prices may go up and down because of exchange rates, or they may have "offers" where they temporarily reduce their mark-up.
I would buy from SBB (either the website or when you arrive), I doubt you could undercut the SBB price.

Yes, sometimes RailEurope will give a decent discount with a discount code. They just had one that expired yesterday, but it was of a dismal amount. Anyway - that's what I'm looking for because I'll be leaving for Switzerland in about a month for my daughter's wedding in Lucerne.

Congratulations on your daughter's upcoming wedding! Since it will be in Luzern, you might want to consider getting a "Tell Pass" instead of a Swiss Travel Pass. The Tell Pass is a regional pass that stretches out from Luzern, the way the Berner Oberland pass stretches out from the Jungfrau. While the Berner Oberland pass isn't offered in the winter, it turns out that the Tell Pass IS offered in winter (November 1 through March 31) and for a discounted price in winter. You can get it for 2, 3, 4, 5, or 10 days at prices of CHF 110, 140, 160, 170, or 220 respectively. (Much less expensive than the Swiss Travel Pass at 216 to 458 CHF.) Here's the link for the Tell Pass where you can see what it covers and where:
http://www.luzern.com/en/tell-pass

Swiss Passes have had fall promos in previous years. Unfortunately, I no longer get any warning if a new deal is coming. Once they go live, available promos are summarized at https://ricksteves.raileurope.com/special-deals/featured-deals.html.