Have a read of what Kevin Sharpe's doing, very similar to what you are suggesting, although his are totally un-controlled.
Yes the nice shiny charge posts with LED's DO cost a lot, how ever there are several reasons they have to, for Highway use they need to pass a fair few tests, they also have to have a fair amount of compliance with different regs, all of which add to the overal cost, theres also the fact that at the moment thier usage is fairly low, but as it increases people/councils/firms wont be happy just to "give" away the electric for nothing (although you are not allowed to sell it for a profit) so there has to be somesort of metering/contol etc buiilt in, theres then the whole safety aspect that needs to be considered etc ............the list is endless really when it comes to having something in the public domain and that any Tom, Dick or numpty can plug stuff into it ..........and sadly this is part of the reason why they cost what they do
Some of the commercial charge posts are already GSM controlled which of courses adds more expense to the units, you then need a back office to run the whole thing again costing more money, eventually I can see them all being on either a PAYG system or where you will just wave your credit card at the post and it will charge you what you use.
Its still REALLY early days I think and there are still lots of folks offering lots of different designs, although they have finally agreed on a industry standard opperating frequency which means all charge posts will work with one card so you will be able to go from one area to another with out issues, where as currently in London I seem to think you cant even go between boroughs
which is just daft.