Did this document include the bit about time lapse for all of the weeks of work they put in? Because they claimed, somewhere, to actually have done a bunch of work, which Doki was willing to pay for if they could provide proof. They put together an item list (sans Storage, lol), but, good point, there's actually no confirmation they did anything beyond the sketch. Still, they might have done something at some point, which is kind of par for the course of someone that works themselves into scamming others. It's... weird, but I've run into that before.
Though the message from the current Manager is pretty funny, because they're kind of correct. If there was an implied contract, it's with the former company.

well, now I look at it, the actual breakdown is even more insane than I thought
On Jan 10, Doki dm-ed the builder
On Jan 13 10:40, the builder replied to Doki with their discord account for contact
On Jan 14 7:59, Doki replied to the artist with Manager 3's discord for her to add
So the builder claimed she is owned 340 dollars, for working from 10:40 AM to 18:40 on Jan 13, before she has spoken a single word to Doki's staff.
On Jan 14- Jan 16, builder and manager 3 work with each other to agree on the final parts and pricing, before presenting to Doki's and the buyer
On Jan 16, she sent over a PDF files, which is basically an "updated components parts", aka she changed some components and her full pricing of 7.2k

From Jan 16 - Jan 18, Manager 3 told her 7.2k is too much, On Jan 18, builder reply she got with one of her contacts and can lower the build to 3.500, making the total $6.6k.

Manager 3 actually pushed back against this $6.6k initial offer, he wanted $6.6k with shipping & tax included.
He decided to include to Doki, but already expressed that he wants Doki to drop the builder

From Jan 19 > Jan 30, They argued with each other and couldn't come up with an agreement
On Jan 30, builder dropped that invoice & calculator. Note that the invoice counted 31/1.... which hasn't happened yet.
Manager 3 didn't read the thing properly and thought the 120 hours, aptly labeled "pre-production cost" was for the mock-up. And demanded a timelapse for why this mock-up would need 120 hours to be worked on.

But if you look at her actual calculation, she started charging from 13 to 31 January....
Tl;dr the 120 hours work wasn't even the fucking mock-up,
she was charging $5100 for DISCORD MESSAGES & TWITTER DMS.