The No to AV campaign, apparently lacking good arguments in favour of First Past The Post, has claimed that AV would cost too much.
Plenty of other commentators have already pointed out that their claims are absurd - including the cost of the referendum itself as a cost of AV is the sort of accountancy that would get you investigated for fraud if you tried it on your corporate expenses; paying a huge amount for unnecessary vote counting machines1 that we wouldn't actually buy; and so on.
The idea that a relatively trivial sum should be used as an excuse not to run a democratic process in one of the richest countries in the world has also been widely criticised, and rightly so. Next Left, for instance, points out that extrapolating the votes in a seat from a statistical sample would be even cheaper - Isaac Asimov's Franchise being the end of that road. (I didn't put cost saving as an explicit advantage of Vote From Hat, but perhaps I should have).
What's been missed, at least in the commentary I've read so far, is that while the principle that democracy is too expensive is repulsive to most Britons, we do it all the time - not in the choice of vote counting system, but in the operation of our vote collection.
At the last general election, there were several cases of disenfranchisement through underfunding - shortages of ballot papers that would have cost more to print; people being turned away from polling stations because local authorities didn't want to pay enough polling staff to meet the Electoral Commission recommended minimum staffing levels; intentionally using inaccessible polling stations; failing to spend time and money reviewing the accessibility of polling stations and fixing the problems, and so on. For some people with disabilities, the idea that it's not worth paying money to allow them to vote is well established.
I certainly believe that if you're going to have a democracy, you can't then put a maximum price on establishing a universal franchise - you pay the costs happily.
If First Past The Post is to be considered superior to Alternative Vote - a stance I disagree with, of course - it should be on the grounds of its ability to democratically reflect the will of the electorate, not on the grounds of cost. But let's apply that to other areas of electoral administration too, not just the vote counting system.
The Meek variant of Single Transferable Vote, because it recursively adjusts the transfer values to get the optimal result (rather than the near-optimal estimates used by other STV variants), can only be counted by computer. Every other vote counting system I'm aware of, including most STV variants, can be done entirely by hand.
A computer-assisted count - using generic laptops or desktops the local authority already has to run a spreadsheet or OpenSTV, not expensive specialised hardware - would make things considerably easier for most Single Transferable Vote variants, Borda, and Range Voting, but even that isn't necessary for Alternative Vote.