https://interestingengineering.com/energy/sodium-home-battery-promises-20000-cycles
Not 20,000 cycles, but 20,000 cycles at 100% depth of discharge. That's a big deal. Lithium batteries offer 10,000 cycles at 80% DOD. If you push them to 100% DOD they are typically guaranteed for half or so.
What that means is that in general, you only use 80% of a battery. If you charge it like Tesla recommends, you only use 60% of the capacity (i.e. you try to keep it between 20% and 80%).
But let's say you use 80%. That means that if it's 25% more expensive, that's still a breakeven on a sodium battery right away, not even counting the long-term savings of get 2X as many cycles.
For perspective: 20,000 cycles, assuming you charge every day and discharge every night (or vice-versa if grid-tied) means that it has an expected lifespan of 55 years.