If you do a PC build using close to the same model parts as the imac from quality brands like asus, gigabyte, corsair etc then the cost comes to about $2000. A Dell 27" 5K screen as the iMac costs ~ $2239. Price is now 4200. I'm talking AUD here so whilst PC is coming in about $1k cheaper once you account for os / software / apple support / longevity / fit for purpose. There's not much in it.
I hate buying old tech but what made me just pull the trigger on one earlier this week is that for my needs the current version is going to smash through anything I will throw at it. Ports wise I don't need thunderbolt 2 let alone thunderbolt 3, but I will certainly use usb3 and the sd card slot and network port.
Also someone else mentioned in the imac form in the last few days (I forget where I read it) that as I've gotten older I kinda have started getting over myself having to have the absolute latest tech and just start pulling the trigger based on what I need.