6.17.1 Artifact Upgrades

Artifact upgrades are a system by which you can upgrade an upgradeable artifact to the next level at a pro-rated fee.  For example, if level 1 of an artifact costs 300 credits, and level 2 costs 600, you can upgrade to level two for a mere 300 credits - the cost of the first level is deducted. 

This only applies if you use the ARTIFACT UPGRADE <power> to <power> command - if you purchase upgradeable artifacts outright they will not be discounted.

Ultimately, a fully upgraded artifact will only ever cost as much as the highest level of the tier.