I've practiced that for many years in traffic. Whether it saved in the long run, I wasn't sure, but sitting and waiting for a clear left can drive a person nuts.
I hope that you’ve saved some money.
If cities can likewise save on public transit fuel, theoretically can help pay for roundabouts.
In fact, since drivers that would otherwise get stuck behind left-turning vehicles might feel gas savings from straight and right-turn driving, local taxpayers can also temporarily help pay for roundabouts.