My group uses the Tech Tokens from AA50. We just hated the idea that you spend all this money, don’t get a single 6 and it’s all down the tubes. At least with the tokens, you don’t have to spend the money again until you get a breakthrough.
You’ve got a good idea too, with the declining cost each turn. Perhaps the best way is the price declines until you do get a breakthrough. When you try for another breakthrough, you have to start over again at 5 IPC per dice.
Also, I kind of think it’s a rip-off that if you get more than one “6” you still only get one tech breakthrough. On the otherhand, could you just imagine a country spending 30 IPCs for six dice and getting 5 or 6 sixes? I wonder how the game would go if one country had all the techs to play with.