9×9 + 7×7 + 5×5 + 3×3
Netherite blocks cost 9 netherite ingots each, so this base is 1,476 ingots — almost never the survival choice.
Every pyramid level reaches one block further out than the level above it. A single beacon therefore needs 3×3, 5×5, 7×7 and 9×9 — 9, 34, 83 and 164 blocks for tiers 1 to 4. Java effect radius is 20, 30, 40 and 50 blocks, and the effect re-applies every 11, 13, 15 or 17 seconds.
Beacons standing side by side can share one base. Four beacons in a 2×2 need 4×4 up to 10×10, which is 16, 52, 116 and 216 blocks. Six beacons in a 2×3 need 4×5 up to 10×11, which is 20, 62, 134 and 244 blocks — enough beams to run every primary power plus a secondary at once. Each beam still needs its own beacon block and a clear view of the sky; glass is fine, and bedrock is fine in the Nether.