Rather sad you'd spend so much time calculating this out.
Now please, do the same for Dell, HP or Lenovo and show us all the amazing innovation they've done recently. We buy hundreds of these at work and I haven't seen anything new in the PC or laptop world for 5 years (or more). Innovation has stalled in the entire PC industry.
Do the same for Dell, HP, and Lenovo? They're are all shipping computers with the latest parts. Apple will soon be 3 Intel CPU generations behind, for crying out loud.
At least Apple have been competitive on screen resolution and disk speed. I don't know why PC manufacturers want to keep stupid 1080p displays and SATA disks alive forever, probably because people always overlook those specs.
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I have a 2007 iMac. It's 9 years old and I don't feel compelled to replace it at all. It runs El Capitan just fine. I'm surprised Sierra is dropping support for it, but I still don't feel like replacing the iMac, because Apple really just hasn't made any compelling upgrades to their Mac line or OS X in forever.
2007 is a bit old. I think your main problem is the low-res display. If you're using that all day, you might want to get something easier on your eyes. Whatever disk you have is also slow by today's standards, but I suppose a SATA SSD is good enough. And OS X does NOT work on HDDs anymore.
My '08 Mac Pro is lasting longer since it's a pro machine and allows expansion via eSATA and PCIe. I can put whatever monitors I want on it. My CPUs are already hella fast. I just can't improve my low RAM speed and can't go past PCIe 2.0 SSDs, which are fast but aren't the best (3.0 is available now, about 2X the speed).