If you're already spending $5k on a computer why does $700 suddenly become not a big deal? Why would you spend more than you need to?
As a business, well I have no experience to go on. Say you need to buy 20 workstations for a team, do you not care that 20×700 = $14,000?
It just seems super odd to not care about value for money at all.
The problem is because
you are the one who is not caring about the value for money.
Lets look at ALL of the numbers. I'll take your post using your exact values. Suppose a $5700 computer was 15% faster than a $5000 computer. Yes, you are correct that it cost $700 more to purchase.
But, suppose that computer is running software that costs $10000 per year (which is actually fairly cheap, specialized software often costs $20,000+ per computer per year). The amount of work that the $5000 computer does in 1 year, the $5700 computer could do in 0.87 years (15% faster works out to needing 13% less time). Thus, you only need to pay $8696 for the software to do the same amount of work. The $700 faster processor saves you $1304/year.
Even more importantly the engineers running that software have a salary + benefits that are probably close to $100,000 / year. That engineer that took 1 year to complete a study with the $5000 computer only needs 0.87 years with the $5700 computer. Again, you save $13,043 in engineer time.
That ONE TIME purchase of $700 saves the company $1304+$13,043 = $14,348 PER YEAR.
It gets bigger when you look at teams. Look at just your 20 workstation cost: 20 * $5000 workstations cost $100,000 and the software costs ~$20 * $10000 / year = $200,000 / year. But that same amount of work could be done with just 17 workstations with ~15% faster processor. Thus you need 17 * $5700 = $96,900 in computer costs. It actually is CHEAPER to buy the team the faster processors. And considering the software, you save $30,000/year. That is even if you don't consider employee costs.
No one in business that
needs this type of power should ever think that a mere $700 more for a 15% boost is even worthy of consideration.