In the breakdown of what's going on in the case from your favourite copyright attorney (I'm not sure if he says it in that video but that's just the most recent update.) The $50,000 bill had to do with a situation where the h3h3 crew switched attorneys in the middle of the legal procedure and the new firm had to acquaint themselves with the case in a hurry, AND file documents with a deadline extremely quickly. At the average rate of a copyright attorney ($200-$300 /hr) plus the fact that they likely had more than one attorney on this case for a few weeks led to an exceedingly high first month and that it's unlikely every bill will look that way.
That said the case itself is fascinating. They're being pretty tight lipped about why they decided to change attorneys but the fact that they did basically led to the following happening:
The guy suing them asked for some pretty blatantly unreasonable stuff during discovery (The amount they earn on every video they've ever put out, how much they filed in taxes for 2016, their bank accounts, etc). They have to respond according to the rules of the particular judge they're dealing with (it goes judges rules > that particular courts' rules > states rules ) and their judge (Judge Forrest) has a 3 day deadline.
Because of the aforementioned change in counsel they missed this deadline meaning whatever the guy asked for is automatically granted.
Their new attorneys had to learn all this and ask for a mulligan and submit their own discovery request in a very short time hence the bill. (sorry if I'm rambling, I eat this stuff up)