Outside of this sale, it's pretty much impossible to get a Sonos speaker for $99 -- unless you're shopping the IKEA line. With the Play:1 (89), you're not sacrificing quality. It's a great speaker, comparable to the Sonos One and Sonos One SL. The only drawback is that it doesn't come with the voice-assistant perks you'll find in the Sonos One, and the AirPlay 2 compatibility that both Sonos One and One SL have.
Another good deal is the Sonos Playbar at $499. While the Playbar (84) offers the best sound of any TV speaker Sonos makes, it's also fairly old. So it also doesn't have a voice assistant or AirPlay 2, and it only supports optical connection to your TV.
If you're looking to create a DIY surround sound setup, you could pair two Play:1 speakers with the Playbar. The Play:1 function as the rear surround speakers, while the bar handles center, left and right. With these prices, that would cost you $697. Or, you can get a refurbished surround sound set, including a refurbished wireless subwoofer, for $1,171.
If you need a TV speaker with a voice assistant and AirPlay 2, the newer and cheaper Sonos Beam ($399) does all of that. When we reviewed the Beam, we found that the smart features made up for the minor audio compromises.
There are a few other discounts in the refurbished sale, so even if you're not in the market for a Play:1 or Playbar, you might want to take a look. For example, the Sonos One is on sale for $159. While that's cheap, we've seen it sold for less in the past.
The refurbished items come with a one-year warranty and free shipping, the same perks you get with brand new speakers.