KSP actually models this well; try putting something into a retrograde orbit and compare how easy it is compared to putting it into a regular orbit. If you fly both well, you'll have less left-over delta-v in the craft that you put into a retrograde orbit (if it makes it to orbit at all).
Alternatively, just switch to "orbital speed" on your navball while sitting on the launchpad. That's what you benefit from if you are launching west-to-east, but what you have to overcome if you launch into a retrograde orbit.
Alternatively, just switch to "orbital speed" on your navball while sitting on the launchpad. That's what you benefit from if you are launching west-to-east, but what you have to overcome if you launch into a retrograde orbit.