Balance for Nexus Extended Promethium Endgame by Karu_Kiruna, on Factorio 2.1 with Nexus-Updated (the 2.1 fork) or with Nexus itself once it has a 2.1 release. Without Nexus the mod does nothing. Source: GreenTech-Solutions/nexus-rebalanced.

What changes

• Prices. Nexus 1.3.0 raised the inputs of 25 recipes up to 133 times and halved the output of five parts. Final products cost at most 3x what they cost in 1.2.9 (never more than in 1.3.4); the parts under them cost what they cost in 1.2.9. Recycling and the copies of rigor-module follow the new recipes.
• Beacons reach the singularity assembler, the matter stabilizer and the two photon enrichment chambers, where no productivity can pass. The other Nexus machines and the omega lab stay without beacons: the omega beacon would push their productivity to the cap, and the lab has no cap.
• Omega lab: research speed 20 (was 2) and 6 module slots (was 4).
• Zero-point energy engine core: its limiter pumps are of its own quality, so a legendary core is no longer capped at the inflow of a normal one.
• Warp drive works only on routes to or from the Oort cloud and Sol; elsewhere it threw the platform through asteroid lines at about 0.6 UPS.
• Storms (Nexus-Threat-Updated): new defaults of its map settings. Instability halves on its own in 3 hours, 0.6 % lightning chance per 1 % of instability, up to 2 attempts per tick. You can still change them in the map settings. A save that had Nexus-Threat-Updated before this mod keeps the values it has; set them in the map settings there.
• Road to Nexus (with razi-protocol): 300,000 km instead of 2,000,000.

Every change acts only on the value it expects: if a release of Nexus changes a number, that change does nothing and the log says so.

Removing the mod from a save: cores of a quality above normal lose their limiter pumps; build those cores again.