I think I recall Karl revealing just how much he gets from sponsors at least once, ironically (or not) in a video about Billy
Found it.

$2700 from this video with about 1m views. It wasn't sponsored but since Karl sponsors literally every video now, we'll take it as standard.
Doing less than 5 minutes of googling reveals that sponsor pay varies widely, but Karl's channel is large and he has a dedicated viewerbase, which is attractive to sponsors. If he returns to regularly scheduled speedtrooning content, I am confident that he will regain about 70-80% of his standard views, probably more in all honesty. All my estimates will be conservative.
Let's just take a starting figure of $2700 with the logic that the sponsor will be at least equal to or greater than the ad revenue, which is notoriously low. Jewtubers often complain about how little they receive from adrev and how sponsors and patreon are "the only way" they can continue churning out slop instead of going to work at walmart.
Karl has over 1m subscribers and regularly gets 1m views. More if he is covering some big drama like the completionist which got 2m.
Some random fags on reddit from a year ago with small channels like 11k subs claim to receive $1000 per "dedicated video". Others claim that the cpm is $20-25 per 1000 views, with a cap at 350k over a 30 day period, which Karl has achieved with his latest Doom video. So we will use that figure as a baseline as well.
I imagine the process for large channels to be something like a negotiation with the sponsor, complete with clauses in the contract that stipulate more or less pay depending on the total amount of views in a given period. Karl would easily fit into the mid tier of negotiating power on the site when compared to the truly massive channels that crack 1m views literally every day, sometimes every 12 hours. Or maybe Karl just gets the standard agreement that everyone else does, except at a slightly higher rate. It's also important to note that Karl regularly accepts sponsorships from Raid Shadow Legends which is the most infamous sponsor out there. They obviously have tons of money to throw around since it's a mobile gacha game or some shit like that, and Karl's channel is about gaming, so it's a win win for Raid to offer Karl a big cpm on their sponsorships.
Using this knowledge, we can estimate that with a cpm of 20 and a cap of 200k views, Karl can expect to make $4000 from a standard sponsor. We can up that to maybe $6000 from Raid Shadow Legends and other mobile slop in particular, so we can settle on perhaps $5000 per sponsor. Remember that Karl is very consistent in output, which is also attractive to sponsors. He outputs at least one video a month, often more like two and sometimes even three, and they usually get at least 500k views, sometimes spiking to 1m and beyond.
So Karl probably earns about 2700/2+5000=6350 per average performing video, perhaps rising to as much as, we'll say a cpm of 30 with a cap of 250k for Raid sponsorships which comes out to 2700+7500=10200 per video, best case scenario.
We also have to factor in Patreon, which according to google is about $6 per patron. It appears as though you can "join" Karl's patreon just by signing into an account, so we'll cut 565 by a third to arrive at 377*6=2262 on Patreon. I also just noticed you can join Karl's youtube channel itself. There is absolutely no way to quantify this since youtube provides no data to anyone other than the channel owner, so we will just ignore it. Do note however that people have joined his channel for 2, 5, and 10 dollars per month. It's not zero, but we'll leave it out in service of being conservative, and it's probably negliible anyway since, who the fuck joins youtube memberships?
Before this whole situation broke out, there were multiple videos of Karl acknowledging the claim that he does the drama grift for money
(click this post for more info, it's large)

Searching through the lawsuit thread, I also came across this screenshot which aligns with my conservative estimates. I imagine the length of the video and average watch time also impact his earnings.
It is also notable that Karl literally sold his house a year or so ago. I really wish I could find the post where someone confirms the address and listing price, but if I recall correctly it was roughly a 1m dollar home. It certainly looks bougie and expensive, and apparently real estate is notoriously expensive in Australia because they have like, two cities, surrounded by a bunch of shitty barren desert. Here is a picture and a link to his tweet:
The lives of me and my family are forever changed for the better because of all of you. You have blessed us and I will be forever grateful. This is us in front of our new house that was made possible by you!
The average mortgage in Australia seems to hover around $4000 on a $600k house. As I type this, I realize I don't know if these are kangaroo dollars or real ones, and can't be bothered to check. It doesn't matter anyway since his youtube income easily covers it. He may have been paying a bit more or less, depending on his down payment. I'm not going to get into estimating his total earnings and potential savings since he started hitting it big on youtube so we'll just say he was paying $4000. Now that he's moved, it may have been reduced to $2000 or so.
All that being said, I believe it is completely reasonable for Billy to expect Karl to be able to arrange with him a payment plan for his debt. Karl most likely makes anywhere from $6000 to $10,000 per video, and frequently releases more than one per month. His patreon revenue increases this by a flat $2200 per month. If it was enough to comfortably pay a mortgage on a house in Australia which looks like that, it is easily enough to arrange a payment plan for a debt judgement, especially considering that Karl smartly downsized his living arrangement prior to the conclusion of the lawsuit. Selling his expensive house was probably the smartest move Karl made in this whole mess.