Researching anything makes other technologies progressively more expensive.  So if you invest heavily in terraforming and then go back to get beams, the beams will cost more.  Reverse is true as well.  However if you continue to ramp up in research capacity per turn you'll still stay nicely ahead of the game.  What it does is allow you to quickly and cheaply invest in targeted technologies, but keep you from just instantly researching everything in creation when it's turn 200.