You pretty much nailed it. They buy and sell on both ends and use Bitcoin/LN as the rails.
Discussion
Who is buying their sats?
Just seems impractical with the current fees. How do they swap to onchain? Can you buy USDC or USDT with lightning ?
Let’s say I want $100.
I create an invoice.
You send me $100 in bitcoin.
It automatically converts and keeps it on the books as $100 on my end.
The use LN as payment channel.