Desktop GPUs have been getting progressively faster, but the difference between a new i7 6700K CPU and a 2011 vintage i7 2600K is about 30%. Unless you're shelling out over $1K for your CPU alone there's not really a lot of compelling reasons to upgrade.

Now if Intel started making more affordable six and eight core mobile and desktop CPUs...

I think this is why I am finding these models so expensive.

They don't really look different to laptops 2-4 years ago. That used to be a huge amount of time performance-wise.