Hi Ed
I'm sure your friend gets asked the same sort of question all the time ie "£XXX? The plumber around the corner said it shouldn't cost more than £YY" Without knowing what the accountant does it's almost impossible to say whether £1,000 is reasonable or not and, without CB, your friend might well be able to find an accountant around the corner who'd do the same work for £500.
Having said all that, if your friend moved his books onto CB AND got his accountant involved, so that he monitored and guided what he did, pointing out errors, then in year 2, 3 etc I'd almost guarantee a reduction in the accountant's work. This is how it's worked with my own practice and, over the past 5 years, for the basic accounts and tax work, I've reduced my fees for the clients I've moved over by between 30% to £50%.
I have no idea how your friend operates or what records he keeps but the typical scenario would be that he takes all his bits of paper and maybe some books or a spread sheets to his accountant after the tax year end and s/he then sorts it all out, puts it into the right order, ties up various numbers, queries anything that's missing or doesn't make sense, and then gets the final numbers transferred into your friend's tax return.
With properly prepared Cloud accounting, where the accountant has kept an eye on the numbers throughout the year and queried or corrected stuff as the months went on, all that year end messing about vanishes and you pretty much should have a near perfect set of numbers for the accountant to take straight into the tax return. This is so much more efficient than leaving a mess till after the year end to sort out.
If your friend doesn't get the accountant involved, or the accountant doesn't like Cloud accounting (there are still a lot of those about) then there's no guarantee of any improvement and, in fact, your client could provide him/her with a bigger mess to sort out.
Hope that helps