One of the reasons it can be challenging convincing someone to switch from console to PC, because that first PC is always gonna have those costs that people typically don't account for; a monitor (more than one, perhaps), a set of speakers and/or headphones, keyboard & mouse... all that can easily add on an extra couple hundred that wasn't factored into the budget.
All that being said, my personal hidden cost that I can't do without now is: my wireless headset. I had a wireless SteelSeries Arctis 7, which I found really comfortable and got so used to being wireless. I tried my wife's Razer Nari Ultimate and they were all kinds of ungodly huge on my small head, so I stuck with my SteelSeries.
After several good years of use, the earcups recently fell to bits so I opted to upgrade to Steelseries Nova Pro Wireless. It's a bit of a lateral move, there are pros and cons to the new ones, but so long as you don't mind using the software to set your EQs and configure your channels etc, they've been a dream for me.
Also, another small silly hidden cost is a good network adapter. I bought one to match my recent router switch (now using these Eero mesh network routers with WiFi 6), and since buying a dedicated network card (with stupid sticky out antennas to plug in), my connection has been consistently silky smooth with no drops. So that's a new thing I can't go without 😅