You haven't even considered how the technology may evolve where it may become more efficient. The solar technology of today could be obsolete and it may be cost effective to upgrade in 10-15 years due to efficiency/cost gains.
As far as solar related jobs you have the manufacturing and delivery of solar panels, all the related industries for raw materials, etc for solar panels and then the installation. That's quite a few jobs.
Also you need to consider jobs outside the US, even the North American continent. Solar may be more expensive than other sources in the US but that's because we have an electrical grid. Solar is the most cost efficient option when considering the developing world, i.e. Africa, parts of Asia, etc. Those solar panels are more likely to come from outside the US, i.e. China, as the dollar exchange value as well as delivery might make it cost prohibitive for developing nations to purchase solar panels from the US.
I'm not so sure that solar is cheaper in the developing world. As these Indian villagers said protesting solar, "we want real electricity, not fake electricity." http://www.eenews.net/stories/1060026477
Solar is not a magic wand. People who couldn't afford to get hooked up to the grid for the last 36 YEARS were gifted a limited solution that cost far more than their little village could afford. The wealthy celebrated by hooking up more appliances than the system could handle and then all the recipients of all this free stuff complain that johnny can't study by the light of the silvery cfl.
When some are just plugging in a lightbulb and a phone and others are plugging in "energy-inefficient televisions and refrigerators" perhaps either the wealthier should abstain from doing so or should instead invest in more capacity.
On a larger scale this would be accomplished with meters and prices that would make using 100x more juice than your neighbor either uneconomical or at least costly enough to build infrastructure but on this scale it would have to have been solved by common sense which like electricity appears to have been scarce.
Solar micro production is insanely expensive. Nobody thinks it will scale even in places like Germany where it's merely expensive.
Grid scale solar is dirt cheap, to the point of being cheaper than coal, but it requires a grid. Not really sure what the point of them highlighting this was. If the villagers had a reliable grid connection, they wouldn't care if it was fed via solar
Efficiency of affordable solar cells can't increase by more than about a factor of 2 from where it is now. Even to do that, we'd have to figure out how to cheaply mass-produce multilayer cells, which are currently expensive one-offs made in labs; I'll be very surprised if that happens in 15 years.
What's more likely to happen, as I understand, is that cells of about the same efficiency level as what most people are using now, or maybe somewhat less, will get much cheaper (e.g., perovskites). But that won't be a reason to replace existing installations.
As far as solar related jobs you have the manufacturing and delivery of solar panels, all the related industries for raw materials, etc for solar panels and then the installation. That's quite a few jobs.
Also you need to consider jobs outside the US, even the North American continent. Solar may be more expensive than other sources in the US but that's because we have an electrical grid. Solar is the most cost efficient option when considering the developing world, i.e. Africa, parts of Asia, etc. Those solar panels are more likely to come from outside the US, i.e. China, as the dollar exchange value as well as delivery might make it cost prohibitive for developing nations to purchase solar panels from the US.