Yes. That's what the "HurryCostModifier" variable is in the Units and Buildings tables.
HurryCostModifier=0 is the baseline. Sort of. (See below.)
HurryCostModifier=-1 means that a unit or building can't be rushed at all. (Wonders, mainly. but this is what you seem to be talking about for the Settler.)
but what you want are positive values. HurryCostModifier=25 means that rushing a unit costs 125% of the normal amount. 50 means 150%, and so on. So if you want a unit to be more expensive to buy than it would be to build, but still be POSSIBLE to buy, then set the value higher.
Now, you can't set it LOWER, because of the -1 issue I mentioned. But you'll notice that most buildings, for instance, have HurryCostModifier=25; that effectively makes 125% the new baseline. So if you have something you want to be EASIER to buy than build, just set it back down to zero.