I recently built this and a few others. They vary in many ways. I think most would agree there are 3 general tiers of building reps and very directional price ranges, YMMV.
1. Beginner Build: Buy a basic cartel watch. Fade the bezel, soften the case and maybe age the dial a bit. $150 to $350 depending on mods or DIY
2. Intermediate build: Cartel watch as base and then do the above stepsm. In addition, Shape the lugs, Cgs. Age dial, relume both dial and hands. Add better crown and crystal. $150 to $600 ish.
3. Advanced Build: Get gen spec case and dial. Do the steps above. Then I see people add gen, crystal and crown. If you go all the way, one might add gen movement and hands. $1200+
Some more examples of beginner to intermediate builds. Sent from my Pixel 3 XL using Tapatalk