Does this mean prices will differ for the "bundled" and paid subscription? This makes no sense.
No, that's not what it means.
If IB showed the low of 468.44 when in fact it should be 467.43 (regardless of whether it's bundled or not), then clearly IB has made a gross negligence on their part.
Maybe. But gross negligence alone is not enough to create liability. Any claim that the broker or data provider is liable is going to be a claim for
breach of contract. And if you are not paying for the data, then there is no contract. You get what you pay for. If you're not paying for it, then the broker has not obligation or duty to
provide the data
at all, and that means that they may not be liable if it is inaccurate.
If it is bundled with something else, one can still argue that the data is provided to the customer as a part of a contract. But I think the claim is a lot weaker when you cannot point to a specific monthly fee. The broker is going to point to something in their TOS that says that market data is provided
as is, with no guarantees of accuracy.
If the TOS explicitly states that the data is provided
at no charge, then I think any claim for damages is extremely weak.
If I give you a wristwatch as a gift for your birthday, and it doesn't work right, and as a result of the malfunction, you are late for a train, and because you are late for a train, you miss out on a fantastic real estate deal and you lose a bazillion dollars, you can't sue me. I gave you a gift and it didn't work. I never promised you anything, and
you didn't give me anything in return. Sorry about your luck.
But if I
sold you the watch, that's a different state of affairs. You now have something that at least has the bare elements of a contract, and there is an implied warranty of suitability, i.e., that if I sell you a timepiece, it is reasonable for you to expect that it will display the correct time, and if it doesn't, then I might be liable.