If it doesn’t already have licenses installed from some other source, the Lumity will require the On In rather than just the On. However, there are often cheaper ways of getting those licenses than buying a new On In.
You can’t reliably buy it new in the US for less than $1000 or so, but that may change since the v2 came out and sellers may want to offload their inventory of v1s. You can buy it used on ebay in guaranteed working condition for $300 or so, or “for parts” (which usually works fine) for less than that if you’re willing to wait and hunt for bargains. But I don’t think I’ve seen it new for less than $750 or so.
Personally, I wouldn’t pay extra to buy it new rather than used from ebay or any other source, because I’ve heard that trying to get Phonak to honor its warranty when you didn’t buy from an audiologist is a nightmare. I’d also be concerned that the warranty on a device intended for sale in Europe wasn’t the same as one intended for the American market, and might not allow me to send it to Phonak’s American service center for repairs. And depending on where these are coming from, the warranty might have started running months or years before I bought it. So if I buy on ebay, it’s with the expectation of having to solve any technical problems myself.
You can search completed listings on ebay and see what these typically sell for. It looks like a few have sold for over $600, but most are under $500, often by a lot. You might make a bit of extra cash by selling 1-2 every few months, but I wouldn’t expect them to sell quickly at that price.