Actually, pricing is one of the least important things to check for a company.
What is more important, and what can influence your manager much better, is to write down, what it SAVES when you have faster/better computers.
Example: Assume to compiler a full build takes 30 minutes on a slow computer and 10 minutes on a fast computer. This saves the developer approximately 10 minutes (assuming he cannot do much useful stuff in the mean time). Assuming a salary of 50 dollars/hr, saving ten minutes saves 50 * (20/60) = 16.67 dollars.
Assume you do 10 builds per week, it saves 167 dollar per week.
When the faster computer cost 1000 dollars more, after 1000/167 = 6 weeks, the computer is paid back.
The complication is that sometimes it's hard to calculate (what if your manager says you can do something useful in the waiting time? Probably you have context switching time loss etc).
But in general, if the faster computer can saves you considerable time, the salary losses outweighs the cost of a computer by far.