I've bought 3 proofing deals from appsumo.

Ashore is awesome. They're lovely people, the automation is really cool, but they're image-centric and their web proofing is buggy.

Quickreviewer is web-centric, but the UI is a headache and the limits are very 2019.

Webvizio is super clean, perfectly lean, has all the tools of the others, works almost flawlessly, has incredibly generous limits at tier 3, and have recently promised all the stuff that matters when someone says "whitelabel".

The team is responsive.
The roadmap is open.
The software works REALLY well.

Considering how well these guys have got it, right out of the gate, I think we're looking at (an understandably high priced) an industry standard, near essential tool for anyone who does anything on the web.
Buying this software now, at this price, feels almost like a crime. It's already near perfect and they've only just begun.

I buy a LOT of stuff here at appsumo.
I recommend only a few.
But Webvizio, for me at least, makes it into the top 5.
Go full stack, and feel super cool when they start charging what this is worth.
If you have ANYTHING to do with design or the internet, then this is a no brainer. Consider it a solid part of your arsenal.

The founders are responsive, and listen to user requests. I'm looking forward to seeing these latest commitments making their way into the listing text.

Buy with confidence. The Webvizio team do what they do well.