Disclaimer: I work in NHS IT. I see this $hit everyday. People need to grow a pair and stand up to their finance/procurement departments and shop around. It's nothing short of lazy and incompetent not to do so.
If NHS trusts are paying over the odds for IT equipment it boils down to one of three things:
1) Incompetence on the part of the procurement departments.
2) Finance/Procurement managers taking back-handers.
3) Just not giving a flying f**k and having no pride in their work.
Pay a visit to your finance/procurement managers house and see how much nice new shiny kit they have, usually stamped with the logo of the company that recently won the "competitive bidding process". Seriously, I have seen this with my own eyes in a previous NHS job. It does happen, far too often and it stinks. I've reported my concerns on several occasions and each time it was brushed under the carpet to save the blushes of the fraudster concerned.
Specialist IT procurement needs to be done by people who actually know what they are doing, not procurement departments who try to overrule IT on every purchase thinking they know where to get stuff cheaper. They know $hit all, and are usually staffed by people too stupid to get a job stacking shelves, only a public sector body could employ these people. No private business would tolerate them, as evidenced by the last fu*kup ad order sent to dell for "200 x Computers" that's it, no spec, no model, no nothing.
I now do all the IT ordering at our department because procurement couldn't be trusted to get it right. We get frankly fantastic deals from most of our suppliers, and pay less than the public rate at all of them. The PCs we buy cost £1200 to the public on the Dell's website, we pay significantly less than half.
As AC @ 12.04 says there also needs to be some parity between comparisons. We, by edict from them upon high in central gov, have to buy encrypted memory pens to 256 FIPS standard, these are considerably more expensive than a standard 4gb memory pen. Often the comparisons that lead to these stories don't think about that, they just see the headline grabbing price figure.