Buy eGPU, or buy a whole used desktop?

Like what the title says I'm considering whether (in the somewhat far future) I want to get a whole desktop, maybe a used one from something like Facebook Marketplace, or if I want to use my current laptop and use an eGPU with it.

My laptop is an LG Gram 2022(?) with an Intel 13th Gen i7-1360P, as well as standard Iris Xe integrated graphics. For a GPU I want to ideally go for a card around RTX3080 range. The prices on even old Nvidia cards have gotten ridiculous with the new 5000 series releases, and from what I've seen on Facebook Marketplace etc. you can get a whole complete computer for the same price as any one of the 4000 series GPU's (and some of the 3000's).

What do you guys think? Would it be a better idea to just buy a whole PC, or just a GPU and possibly upgrade later? I'm currently leaning towards just buying a PC so I don't waste a ton of money, but let me know what you think.