The total cost of the Voyager mission from May 1972 through the Neptune encounter (including launch vehicles, radioactive power source (RTGs), and DSN tracking support) is 865 million dollars.
and
A total of five trillion bits of scientific data had been returned to Earth by both Voyager spacecraft at the completion of the Neptune encounter.
That's $0.001384 per bit. There are 1120 bits in an SMS message. That's about $1.55 per SMS. Not exactly cheap, but then Vodafone don't have coverage beyond Pluto.
I mean, a chess computer has no concept of a plan,
That really depends on the program, now doesn't it? I'd be very surprised if the programs didn't cache some of their computations to immediately generate the countermove if the opponent moves as expected, and use the reminder of their turn to further simulate future moves. After all, it's an obvious optimization, and that's what plans are - now I do this, then he does that, then I respond with this move, and so on.
That's not what I'm talking about. I am a club player of moderate ability - I would have no hope against a modern chess programme like Fritz on a basic PC (even on that hardware, it's at least comparable to a top-50 player). However, I can look at a position and decide that to win, I need to, say, get my knight to a particular outpost, and drive home a passed pawn and promote it. A computer doesn't think like this.
and even Kasparov or Topalov or whoever can only calculate a handful of positions a second.
I wouldn't be too sure of that. A brain is basically a massively parallel computer, simulating the likely events in your immediate vicinity all the time - and in the case of humans, using abstract thought to simulate far away places as well. It's likely that there are hundreds, if not thousands, of plans that are considered subconsciously but rejected because of some obvious flaw, freeing the conscious mind to only examine the most promising ones in detail.
I was talking about brute force computation, which has been measured. I forget the precise result, but I think you're talking something like 3 or 5 positions a second. Those players, and even I derive most of our ability from pattern recognition, while the computer is powerful because it performs an (optimised) search on a tree of possible continuations. There's a fundamental difference in how humans and computers play chess.
Draughts has only been solved on the 8x8 board, and the best programmes for the 10x10 version caught up with the top humans a few years back.
It's interesting to speculate about how the advancement of playing software might hint at how tactics and strategy are balanced for the various board games. I mean, a chess computer has no concept of a plan, and even Kasparov or Topalov or whoever can only calculate a handful of positions a second. Of course, the most interesting part of that problem is how to pose the question.
It seems that more and more mathematicians are using a new, high level language named "research student".