Unfortunately, it can be tricky to find dirt cheap. Used ones generally go for around $130 these days. The top mainstream CPUs in an Intel generation have a knack for retaining a significant amount of value; the 3570k can be found for just $40.
It was a fun CPU; I ran my 3770k until some issues with the USB controller motivated me to upgrade it in 2018. But I'd be hard-pressed to tell you it's a good idea at this price when you already have a 3570k. It being a pre-built is also a complicating factor since there will be rather poor motherboard documentation.
its for my wife ill spend the 80$ happy wife happy life they say haha im giving her my old pc because im building a ryzen 5 one https://pcpartpicker.com/list/XWPbFG
because its like 80 more dollars haha but maybe i could get away with the ryzen 5 2600x
i also got a gtx 970 i own already and a corsair 750 watt psu going along with it also