These situations are really difficult to fight when you purchase shipping through eBay because you're using eBay's UPS account instead of your own.
Have you gone through the process to appeal the surcharge? I don't know if you can do that yourself since it wasn't your account or if you have to go through eBay CS.
In your shoes I'd contact eBay CS through their social media channels (US-based reps) and ask for their assistance appealing the surcharge. eBay for Business on Facebook or Askebay on Twitter.
You appear to be within UPS limits, so something with either weight or dimensions measured en route (possibly an error) triggered the charge. I would try to appeal citing that your package didn't exceed the limits.
$1,050 surcharge is the 2023 rate for exceeding UPS limits:
Packages can be up to 150 pounds.
Packages can be up to 165 inches in length and girth combined.
Packages can be up to 108 inches in length.
Packages with a large size-to-weight ratio require special pricing and dimensional weight calculations.
When you go to this page (link) which offers packaging guidelines and select appliances or power tools, enter your box weight and dimensions, it kicks back an alert that the limit is 130 pounds. But that appears to be based on box size and weight guidelines and not a category limit, unless I'm interpreting it wrong.
