To me, it seems what they're doing with this title is somewhere between testing the waters and a soft launch.
Bear in mind that the staff turnover at major labels is so high that there's probably no one still around who was part of the DVD-A/SACD 5.1 push 15 years ago, so the idea of selling a standalone 5.1 music release on Blu-Ray is probably basically uncharted territory for a major label right now.
So rather than press up tens of thousands of copies of this without knowing what the demand is going to be like and risk having them hit the cutout bins, they press a fraction of that number to gauge interest. Presumably for a band as big as Coldplay a Grammy nom in the 5.1 mix category is pretty much a sure thing, which will basically act like free advertising for this release. So if this initial run sells out and the Grammy nomination comes in, I would think that would be the impetus they need to press more copies.
A couple of positive signs though, for the optimists amongst us:
The fact that the disc is already hard to find is a good thing. If stores don't have copies, they'll be asking the distributor for more copies and if the distributor doesn't have any more copies they'll be asking the label for more copies which will make them aware of the demand.
The fact that this release exists at all means there's someone in the Coldplay 'food chain' that "gets it" with regard to 5.1 music. A standalone 5.1 mix (and a real 5.1 mix at that) in an economically priced standalone format is such an anomaly these days - they could have easily stuck this in a 'deluxe edition' reissue of the album or something for $100. Coldplay are one of the biggest selling acts of the last 10 years or so, so the sales of this disc are going to be a drop in the bucket compared to the stereo version - obviously the music business is about making money, but if they wanted to exploit this 5.1 mix more cynically as a moneymaking venture, they definitely could have done so. So I would take it as a good sign that they're trying to make this Blu-Ray widely available as cheaply as they are.
In conclusion, I can't believe I wrote this much about a band who's music I don't like at all, but I feel like this release is a really positive thing for the format.