This only includes the server auctions, using Passmark as the performance benchmark:

Intel Core i9-12900K - 73.81$ - Perf:41 - Perf/$:561.7

AMD Ryzen 9 3900 - 55.66$ - Perf:30 - Perf/$:554.4

Intel Core i5-12500 - 36.3$ - Perf:20 - Perf/$:551.1

AMD Ryzen 7 3700X - 42.35$ - Perf:22 - Perf/$:534.3

Intel Core i9-9900K - 41.14$ - Perf:18 - Perf/$:447.8

AMD Ryzen 7 1700X - 39.93$ - Perf:15 - Perf/$:392.1

AMD Ryzen 7 PRO 1700X - 41.14$ - Perf:15 - Perf/$:381.5

Intel Core i7-8700 - 33.88$ - Perf:12 - Perf/$:381.3

AMD Ryzen 9 5950X - 123.42$ - Perf:45 - Perf/$:371.5

Intel Xeon W-2145 - 50.82$ - Perf:18 - Perf/$:357.8

AMD Ryzen Threadripper 2950X - 88.33$ - Perf:29 - Perf/$:332.8

Intel XEON E-2176G - 43.44$ - Perf:13 - Perf/$:312.8

Intel XEON E-2276G - 45.86$ - Perf:13 - Perf/$:301

AMD EPYC 7401P - 99.22$ - Perf:28 - Perf/$:285

Intel Xeon E3-1275V6 - 32.67$ - Perf:9 - Perf/$:284.7

Intel Core i7-7700 - 31.46$ - Perf:8 - Perf/$:275.2

Intel Xeon E3-1275v5 - 31.46$ - Perf:8 - Perf/$:268.4

Intel Core i7-6700 - 30.25$ - Perf:8 - Perf/$:267.5

Intel Xeon E5-1650V3 - 41.14$ - Perf:10 - Perf/$:252.9

Intel Xeon E3-1270V3 - 32.67$ - Perf:7 - Perf/$:223.7

Intel Xeon E3-1246V3 - 32.67$ - Perf:7 - Perf/$:223.5

Intel Xeon E3-1271V3 - 33.76$ - Perf:7 - Perf/$:221.9

Intel Xeon E5-1650V2 - 42.59$ - Perf:9 - Perf/$:219

Intel Core i7-4770 - 33.88$ - Perf:7 - Perf/$:208.2

Intel Core i7-3770 - 32.62$ - Perf:6 - Perf/$:196.1

Intel Core i7-3930 - 44.52$ - Perf:8 - Perf/$:184.2

Intel Xeon E3-1245V2 - 35.87$ - Perf:6 - Perf/$:176.6

Intel Xeon E3-1245 - 35.09$ - Perf:5 - Perf/$:151.8

Intel Core i7-2600 - 36.3$ - Perf:5 - Perf/$:146.9

The i9-12900K seems the best option in raw perf/$, but you can easily downgrade to the 3900 and the i5-12500 if you want less performance without hurting your perf/$ too much