My searches so far show insane differences between insurance rates and cash rates. The cash can be 5-10x higher than what the insurance company pays.

It seems like a clear case of systemic fraud to me. Am I missing something?

Also I am not able to find any fundoplication or LINX (43284).

Many hospitals don't discount from their list price for self pay. Medicare pays ~10% of list price. So, for example, if there is an insurance rate set at "130% medicare" (common to have a coefficient between 1 and 2), then yes, you'd still see many cash rates that are 5x insurance. However, many hospitals also listed Managed Medicaid insurance rates. These are generally 3-5% of list price & look for similar to normal insurance plans. So, what you're seeing may also be comparing a Medicaid rate to a very high cash rate.

Will add 43284 & other gastro procs shortly. Thanks!