I am certainly not trying to convince anybody to anything, I am just stating the fact: If you are net positive (your PV production is more than your total consumption) than you are charging for free. If your PV production is less than your total consumption, the charging is not free.
According to your post, you are falling into the first group (good for you) and you are charging for free. I am in the second group, and for me charging price is the same as the utility price.
One other thing to note, if you can get the usage to near zero net or down appreciably there is another advantage. You normally pay utility bills with after tax money. When you pay for a solar system you get tax credits while prepaying for the opportunity to collect energy. One person I worked with compared it to an annuity, but the benefit you get won't be "taxed" while a stream of income generally would be.