Good suggestion, but many people are happy to pay someone to do a task which they have no interest in, and the process of which may be highly foreign to them.

I've seen plenty of folks use a CMS to completely botch up their site, suck up 6 hours of their time, and end up worse off than when they started.

If someone is making continual changes, the CMS makes sense. If it is a business that does 1 or 2 updates per year, it might be better to outsource the web stuff.

I've had little success with CMSs. People find them too complicated and I end up either holding their hand, fixing their mistakes or just doing the update. For free.

How much do you value your evenings at? £250 would be 1-2 evenings. One evening and it seems like reasonably easy money. Two evenings and suddenly its not quite so generous. Surely any technical person can charge $50 an hour? My day job charges me out at $1000 a day. I have also found that when it is an amount less than that I tend to resent the fact that I've had to give up an evening.

Stand up for yourself. Charge an amount that makes you happy.

A CMS brings in additional complexity of updates and security breaches, which can cost much more than a $400 update fee a few times a year.

Content changes could require new CSS styles (which would require a new round of cross browser testing), image editing, and cleaning up mal-formed text from an email or Word doc. You also need to factor in how much you should charge to make it worth your time to come up with an estimate, fire off an invoice, etc.

If clients are paying this price then it sounds like his pricing is correct.