Lane keeping is not what EAP does. EAP offers auto steering. Can you give specifics in terms of what you mean by that it's unreliable? I've used EAP for over 1600 miles on all sorts of road and traffic conditions and I can verify that it does an excellent job of staying in the lane. There are many times when the people in front of me where drifting out of the lane on a sharp curves but my Model 3 was still in the lane. Is it perfect? Of course not, but is there something that does it better than EAP right now?
You can't just compare TACC on other vehicles to EAP. EAP includes TACC, auto steering, auto lane changing, auto parking, summon, and potentially more with future updates. Is there an equivalent to EAP from another manufacturer right now that you can get for $5k?
With technology you always pay a premium for getting something that no one else offers. Think about an iPhone. Are there other phones that does a lot of similar things? Of course. But there are a few things that the X does that other phones don't and people pay a premium ($1k) to get those few things.