Why is anime so expensive to make? It's not like I thought that anime could be one thing that one group of people could easily decide one day to do, but costs are seriously way bigger that I could have ever imagined, as shown here for example, what's worse is that making a simple episode can even be more expensive than that, as shown here, it can even go up to 300,000 $ per episode.

It literally says.


  An anime episode can cost between US$100,000 and US$300,000 to produce.


That maximum is around 6 times bigger than what I thought an anime episode could cost at most (considering that what's animated is a top series, with top animators, top animation programs, top voice actors and so on).

All costs shown on first link are around 3 to 10 times bigger that I would have expected, so I'd like a general explanation, prefarably using the costs shown in first link as a base, of why it is so expensive to make.

Thanks.
As animated television goes, anime is actually made on the cheap. This article goes over the costs per episode of a few different US animated shows; every one of them is more expensive than the cited high-end cost of $300,000 per episode for anime. 

The Simpsons seems to be top in costs; according to the article, it cost around $2 million per episode in 2007. A 2011 source indicates that voice acting costs per episode alone were around $300,000, and that was after the actors took a 30% pay cut, coming down from a high of around $440,000 per episode. That means The Simpsons was paying more per episode for voice acting alone than the entire budget of an average anime episode.

As for the rest, Nickelodeon apparently spends around $600k per episode on their animated shows; the sources come from comments made around the release of TMNT, but a post in a forum cites a Wall Street Journal article that I can't read because it's behind a paywall claiming that Spongebob too is around $600k per episode. I was shocked that Drawn Together got $700k per episode since it was widely regarded as terrible and was canceled. This Cineeuropa article claims that the average hour of US animation in 2007 cost €776k (about $800k today). 

An Answerman column from 2015 also goes over this and offers some conjectures about why: US animators get paid more, thanks to unions and other market factors, and voice actors, like other television actors on US TV, tend to make more money as the show goes on longer, as we saw with The Simpsons. In another 2015 article, ANN reports on a study finding that animators in Japan make around $28,000 a year, which is a very modest salary in the US. This 2009 article goes into more details on staff salaries in anime. Another Answerman column touches on voice actor salaries in Japan and mentions that most voice actors make between $120 and $360 per episode, though the more famous ones can set their price.

So anime are not really that expensive to make, in terms of the usual cost of producing a professional level half-hour animated television show with top talent.