ChipFlip
The Ryzen 7 5700X3D costs 2.25x what the base Ryzen 7 5700 does used, $315 against $139.99. Same core count, same socket, same generation. The entire $175 gap comes down to one thing: a stack of extra cache bonded onto the chip.
What 3D V-Cache actually does
AMD's X3D chips stack extra L3 cache directly onto the CPU die. More cache means the processor pulls fewer round trips to system RAM, and in games specifically, that translates to real, measurable frame rate gains, sometimes a large jump depending on the title. It's not a universal win. Outside gaming, in general productivity work, the extra cache barely moves the needle.
The base 5700 is not a weak chip
Eight cores, sixteen threads, a totally normal AM4 part that handles everyday computing and plenty of games without complaint. It won't chase the frame rates a 3D-cache chip hits in cache-sensitive titles, but "won't hit peak frame rates" and "struggles to run games" are very different claims. The 5700 is the second one only if you're comparing it directly against its own X3D sibling.
Is $175 worth a cache stack
Depends entirely on what you're building. A dedicated gaming rig, especially for titles known to respond well to extra cache, can genuinely justify the premium. A general-purpose or budget build usually can't. This isn't a small purchase decision to hedge on: pick your use case first, then pick the chip.
Bottom line
If gaming performance is the priority and the title list leans cache-sensitive, the 5700X3D earns its price. If you're building something more general-purpose, save the $175 and go with the base 5700.