Usually merchants accepting Bitcoin will need a lot of INBOUND liquidity. That means many of their customers could open a direct channel, private or public and pay them using that channel. That will involve 0 fees.

Merchants usually are encouraging customers to open channels towards their public node but that doesn't mean they should not put high fees on their outbound channels, to avoid drainage for those that are using their node for large swaps or rebalancing.

Keep in mind that their outbound channels are also used to make swaps and "empty" the channels making more space to receive.

And now we have also inbound fees too that you can play with. There are many ways to play around with fees as a merchant node but I do not see them using high fees policies as a way to "earn more sats" but more to control the flow of the liquidity in their advantage.

We will see more merchants using decoy nodes, in front of their real LN nodes, protecting in this way their liquidity, with private channels.

That's just an extra step vs. charging high fees directly on your product/service, and the merchant would have to curate their inbound liquidity as @DarthCoin mentioned

Just because it's less transparent doesn't mean the buyer won't catch it, for instance in ShockWallet (and I think most LND based wallets) we have sane defaults that will error if there's gauging on routing fees when you attempt a payment

Nothing stops fiat merchants today from charging excessive fees. They tend to not do it because its bad for sales.

Imagine if every credit card terminal had to be built and maintained by the shop. They'd probably all break in less than a year.

Furthermore, imagine if every shop had to secure their own intra-bank settlement contracts so the money could actually get to their account. I imagine the local butcher/baker would have a difficult time figuring that out.

This is why no pleb store is gonna fart around with sovereign LN. They'll just outsource it to a bank or payment processor like the do today with fiat.

In this scenario, the merchant is pretending to have an expensive intermediate with no alternative?

The merchant may get less business if they make it too expensive just to pay them.

You do highlight a possibility in the future where merchant nodes are held hostage by intermediates to receive payments. One would expect that those willing to make these payments in the first place might also open direct channels to the payment destination. But this is not always economical.