I have seen different posts on suggestions for this Tech, but none have quite been as simple as this.

I think that Hyperspace tech should reduce the cost of deut for flight of the Hyperspace drive engines, and only the Hyperspace drive engines.

The way i would suggest this is by going a % by level like Plasma tech does for income, and Ion Tech does for Deconstruction.

the % i would suggest would be between .33% per level and 1% per level, that way it doesn't get too out of hand towards the later parts of the universe when people have extremely high tech levels, causing the Hyperspace drive ships to fly for free basically.