A suitable UPS for that application costs less than $100.
My $200 1500VA/1000W CyperPower UPS could handle a short one or two hour storm, but storms can last for 10+ hours here during the wet season. One long power outage could cost me a lot more than $1000 in basement damages (my basement is finished).
A comparable all-in-one product to this pila battery would also be around $1000: https://us.ecoflow.com/products/delta-2-max-portable-power-s...
You can easily cut that in half shopping for an inverter and battery separately:
$240 for an inverter: https://www.homedepot.com/p/VEVOR-2500-Watt-3-4-HP-Sump-Pump...
$200 for a battery: https://www.homedepot.com/p/Basement-Watchdog-Maintenance-Fr...
But a lead acid battery might last 5 years where the pila battery is designed for 10+ years, so you're looking at $400 total on batteries. That quickly gets close to the $1000 for one pila battery.
I want to believe $100 is all you need, but to me the math with the numbers that I've seen suggests $1000 is not unreasonable for something like this.
That unit is more powerful, higher capacity, and has more solar features than the Pila product. The Pila is also $1300 after pre-orders are over.
I'd pick the Delta unit, personally. They go on sale and you can even grab them from local places like Costco with good return policies.
My experience with sump pumps is low wattage and intermittent use. Sounds like this does not correspond to yours.
Pila is great value.