The key rule involves the neutral-to-ground bond: Only one bond point avoids parallel paths and GFCI issues. The inverter becomes the source and must set a stable reference. Adding a battery complicates grounding.
Your inverter does not appear to supply it (smaller inverter-only units often don't). You will probably measure significant AC voltage between G and N at the inverter.
Recent pricing trends show standard industrial systems (1-2MWh) starting at $330,000 and large-scale systems (3-6MWh) from $600,000, with volume discounts available for enterprise orders.