If you're playing TA, tech costs (relative to the galaxy size modifier, not the costs in the XML files) have been increased across the board; if memory serves, Gigantic/Normal DA is equivalent to approximately Gigantic/Very Fast TA. Apologies, I don't have my notes accessible. Playing on Immense increases tech costs further, of course-but it also increases your score, all other things held equal. However, it does not increase your planet count-and in fact galaxies in TA have less maximum planets than in DA, and tend to have less planets on average as well-even regardless of habitable settings.
Also, offensive techs (red techs-not purple) in TA have been given a hidden modifier to increase their cost (at one point in time by 50%, although I'm no longer sure if this is a valid number); this applies not merely to weapons but also to planetary invasion technologies.
Additionally, tech inflation in TA is far more severe than it was in DA-in DA, tech inflation capped at ~2.75x as much as the base cost (going from memory, apologies if it's slightly off), whereas in TA, by the time your first ~50something techs are researched, you will have maxed out your tech inflation, with a new research cost of roughly 6x base cost for offensive techs and around 2.8x for others.
The bottom line is that if you're playing TA you're effectively crippling yourself by playing a slower tech speed-things are already slowed down more than enough-especially with the new prerequisites for a number of rather basic techs.
Finally, while many players have shown us tricks to use against the higher difficulty AIs that the AI can't deal with (blind spots, if you will), by making use of the hidden research bonus for the player on higher difficulty levels, it's really not strictly necessary to use these "loopholes"-unless of course your aim is maximum score (in minimum time, as game length detracts from score).
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