IMAC access Wi-Fi 6E?

Not according to the linked page at the top of this screen…

What you need to use Wi-Fi 6E

To join a Wi-Fi 6E network, you need one of these Apple devices:

• iPad Pro 11-inch (4th generation)
• iPad Pro 12.9 inch (6th generation)

if you mean if the imac can connect to a wifi router that support 6E then it should if the router also has the 5Ghz and or 2.4Ghz band, doubt many routers would exclusively work with devices that native supported 6Ghz

And the prices I have seen for recent Wi-Fi 6E routers is between $499 - $799 USD. Quite happy with my new Synology RT6600ax and Wi-Fi 6 priced at $375.