Where are these theoretical models? Surely the low barrier of entry to creating a node would prevent running one from being so profitable?
No idea about theoretical models, but surely that means you could have more income by charge fees when people route transaction through your channel/nodes
What is the barrier to becoming the 1st most connected node if the cost is only $2,000? Is it extremely time intensive to set up channels? Marketing?
If you have more Bitcoin on your LN channel/nodes, that means you can route transaction with big value and you even can even charge small fees.
The fastest way to become most connected nodes is by becoming merchants or services, that way customer would connect to your channel/nodes if they couldn't find any route to your channel/nodes
Why isn't everyone doing this and driving the returns down at rates like that?
Because LN isn't ready for mainstream users and even LN developer don't encourage user to use LN on mainnet.
My thought is you shouldn't use run LN channel/nodes solely for profit by charge fees when people route transaction through your channel/nodes since LN supposed to have low/zero fees and i doubt it's worth your time unless lots of people connect to your channel/nodes.