I doubt it's actual nothing, rather I think the added cost in absolute value is used to improve operating margins in ratio. This would also drive internal incentives, and it's rendering the cost to the manufacturer irrelevant so long that the capitals at hand and market demand can absorb it.

e.g. $150 TV + $75 chips - $100 rebates = $125 -> negative cost and +10% margin to add chips!

And the problem is that we as customers are still charged the full $225, not the essentially nothing.

I do Bluetooth hardware for my job. At the scale that TV manufacturers operate at, I would be extremely surprised if Bluetooth cost more than a dollar for them to implement.

I operate on the scale of hundreds to thousands of units, and Bluetooth adds less than $5 to each unit. At millions, I assume it's more or less free.