Microsoft's fails again
There are a number of relevant issues not mentioned here. For one, upgrading an XP system also will require upgrading all the software, which can easily outweigh the costs of new hardware, if even at all possible. So, the generic options in this column of all possible upgrade paths are not really anything but a market survey presented as advice. Also, many vendors chose to discontinue driver support after XP for printers, scanners, etc. so that would also have to be replaced. These are all tangible costs and wasted time versus *potential* security risks that no one can predict.
Also, having just installed two new XP machines in the last 6 months, I can say with certainty that the performance of XP on any given machine is much better than Win7 or Win8. It is much faster, more responsive and works great, even with the 4GB limitation of 32-bit memory addressing, because it is a simpler and slender OS. XP was a major technological achievement after Windows 95 and 2000 and represented the best and most modern OS architecture ever developed.
What is truly amazing is that the IT industry and its pundits have a terrible record at predicting calamities (Y2K !) and not predicting real threats (malware) and generally seem to be unaware of what many users actually experience and are faced with. This comes from the 'orifice' arrangement as noted by Steve Jobs where most IT products are purchased by someone for use by someone else, so that the industry perceives a distinction between users and customers. Thus, many 'customers' don't give a crap about user problems, convenience, or wasted time, which feeds back to terrible products produced by the IT industry. Win8 really comes to mind here, as well as so many other products/platforms that are more about strategic market share of vendors than actual user functionality. Perhaps the best evidence for this is the 30% market share of XP to this day, which does not scream that the OS needs to be replaced, but that this OS is doing its job very well. What companies like Microsoft are truly blind to is the great service these older machines are still providing on a daily basis, which does not seem to get recognized or used as a positive marketing tool for Microsoft, though it is the most powerful and compelling economic argument to use MS products. This is the blindness at MS that has prevented development of products that XP users would have migrated to, so I see it as an abject marketing failure by MS that the adoption rates for Win7 and Win8 are so low in the product lifetime cycle compared to XP.