How can companies still get away with not shipping these cables in the box with displays?
But what happens next? They ship their TV to Best Buy, who quickly notices the TV ships with an HDMI cable, "robbing" them of the chance to sell a Monster cable. Or worse, the customer might still buy one, get them both home, notice there's no difference (or at least no $400 difference) and return the Monster cable. Ack! That's a $100+ profit opportunity that Samsung is costing them. How will Best Buy make up for it? They're going to jack the price of the Samsung TV up by some fraction of the $138 that they can no longer make. Not necessarily the whole amount, it would be prorated based on the average rate of Monster purchase; Best Buy has its own problems if it jacks the price of a TV up as it is a competitive market for them, too!
In fact, it is so competitive that it is not hard to imagine that Best Buy will discover they can't effectively sell that TV for ~$50 more (guessing) and just plain take it off the market. I am not saying this is inevitable, just that it is definitely a very possible outcome. If they don't, the very-price-sensitive American consumers will certainly notice the price difference in sufficient numbers to reduce sales of that TV.
So, how does this feed back to Samsung? They put in an HDMI cable, and either their retails sales drop, or Best Buy even entirely drops their TV.
So, whose fault is this? Money grubbing Samsung? Money grubbing Best Buy? Well, the capitalistic model tends to assume that the customer is informed, and when the customer is not informed, they can be scammed. Here, the customers are not informed. So I split the blame between Monster, who are aggressively lying to customers, and the customer base itself. (Best Buy to some extent here too, for the same reasons as Monster.) Not one, not the other, both. Too many audio/videophiles will aggressively defend their purchase of expensive cables, even after it is explained that their justification is technical gibberish, and as the market leaders they deserve some of the blame.
The other reason I blame this is that if you resolve the problem that a critical mass of customers actually believes expensive cables work, the problems go away. Best Buy raises the prices of all TVs a bit to make up the profit margin, as do all similar retailers. (Most are working on single-digit % profit margins from the top corporate POV, so if they lose something like the Monster cable they will need to make it up elsewhere.) Customers don't even notice because TVs continue to work like computers with constant price drops, so it manifests as a brief interruption in otherwise-falling prices rather than a huge, visible increase. Samsung starts sticking cheap-but-effective cables in, and instead of being punished by the retailers, customers reward them with happy thoughts about good service and a good out-of-box experience (which are hard to quantify but certainly produce bankable assets in the end).
The other option: When buying a TV through a different channel where there isn't a good Monster upsell opportunity, perhaps something like Amazon (which still has the upsell opportunity in some sense, but will present customers with many 1-star reviews and give them a chance to become informed properly), ship an HDMI cable then.
Second order effects, second order effects, second order effects. Always think second order effects when thinking about economics. It's never the simple story, the economic entities react to each other.