As someone who recently built/rebuilt a PC from the top down (mid range ryzen 2600 build with ram headroom for Daz) it isn't cheap but you get significantly more bang for buck buying parts, yes it appears more expensive but you get three important things that most prebuilds never have.
1:Full control of parts you buy, no compromises on PSU or expansion slots, get the exact GPU you want, the mobo you want ect., i can't stress how important it is to have the room to expand, even having room in the case for extra HDD's matters a lot more than you'd think and pre builds tend to cheap out on at least one of these things.
2: Prebuilds are "time locked", they are put together and shipped and priced as such, a self build isn't, you can order a part when it's cheap or you find a deal and progressively collect parts, i did this and saved probably around £100, mainly on ram (£30 off due to a deal, making 32GB significantly better £/GB than the 16 i was considering, and at 3200 speed to boot rather than 2600)
3: you can reuse your old parts where possible saving decent money, network cards, old HDD's, optical drives, case fans, hell the case itself, all are small change individually but they add up pretty quick, save your money for the GPU and CPU that are the real cash holes.
I know self building is intimidating but really it's not that bad, i'm no pro, I've mainly been a part switcher but the step up from that to a full build isn't as much as you'd think, if you've ever switched a cpu/cpu cooler then your good for at least a try as there isn't much more taxing than that to do. There are countless decent build guides out there to watch and read as well so you're not going be coming at it cold and without any idea what to do.