I would go for the ASHPD, too. As others have mentioned, it would revolutionize travel. The cost savings/economic potential for even just one pair of portals would be extreme in space travel. Sent a couple of satelites that aren't much more than big pieces of cardboard with station keeping systems into various orbits or to any place (in the solar system) we want... the biggest headaches in rocket science have just been solved. Oh, also no threat of meteors anymore, since we can put engines on them to push them out of our way far ahead of them becoming a threat.
Even if the portals conserve energy(i.e. stuff going through to places with higher potential energy will mean a consumption of energy at the portal device, my own pet theory of how it works
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), the actual energy cost - if we get to spend it on/as electricity - would be lower than minimum wage in industrialized countries is.
About the moon dust issue: portals seem to work on many different surfaces. Of course CJ or GlaDOS could have had office walls painted with moon dust containing paint for arbitrary reasons, but since were are never told that its the only portal conductor...
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edit: I mean, seriously, does anyone believe they put this special moon dust paint that cost a fuckton of dollars to make on arbitrary surfaces in places were no one was supposed to be, ever again? In places that had been constructed long before portals were researched? (Or anyone had been to the moon...)
And one more thing to think about: iirc at the beginning of the first game Chell is let out of her chamber via portal... and it dosn't look like there is a portal device around. So obviously portals between static places can be built, too. Every form of transportation will get much, much easier and cheaper. At the cost of a huge number of jobs, though. But its staggering to think about how many more ressources we could spend on improving the quality of live of all humanity, now that we have unlimited instant travel that takes only electrical energy and very (hand-)portable infrastructure.