50% is just something I tossed out. As 1k plus beakers is easily achievable in the last fifths of most games, it is overpowered.
I had considered a graded schedule where the first 100 beakers overflow is returned at 1-1, and it reduces beyond that.
This also discourages some of the tile shuffling that may occur.
Alternatively, do overflow, but at a reduced rate (ie: not full overflow) as I really don't think tech pace is an issue, though this i largely a balance issue that can be changed at anytime.
For all we know we could see 50% increase in tech cost in a future patch with full overflow. heh.