The tech cost multiplier affects the adjusted base cost, and the capital also gives the tech penalty, so with 6 cities on standard size the tech would cost 110*1.3 beakers.
Let base cost be 1 beaker, then the tech cost formula is
1 + 0.05 * n on Small
1.1 * (1 + 0.05n) on Standard
1.2 * (1 + 0.03n) on Large
1.3 * (1 + 0.02n) on Huge
Quick table for 1-15 cities
Code:n Sm Std L H 1 1,05 1,16 1,24 1,33 2 1,10 1,21 1,27 1,35 3 1,15 1,27 1,31 1,38 4 1,20 1,32 1,34 1,40 5 1,25 1,38 1,38 1,43 6 1,30 1,43 1,42 1,46 7 1,35 1,49 1,45 1,48 8 1,40 1,54 1,49 1,51 9 1,45 1,60 1,52 1,53 10 1,50 1,65 1,56 1,56 11 1,55 1,71 1,60 1,59 12 1,60 1,76 1,63 1,61 13 1,65 1,82 1,67 1,64 14 1,70 1,87 1,70 1,66 15 1,75 1,93 1,74 1,69
Will need an expansion update to provide beaker comparison for the T-hawk huge game.