Even if your designers are getting poverty wages of 35K, a 5K workstation investment is still only a tiny tiny slice (less than 3% in this case) of the company's investment in that worker.
Going cheap on a 35K worker and wasting 8 hours a month of their time would cost the company $1,615 every year, or $8,077 over the course of your 5-year projected equipment lifespan. And that's for each employee. If you have a team of five "charity" workers at 35K, throwing only three hours downtime per month due to crap systems will cost your company $15,144 over that equipment's lifespan...
Only if you're getting your labor for free does it make sense to cheap out on hardware and let your people deal with the consequences!
That being said... you may find that, for your company, there is a sweet spot of investment vs. performance and an acceptable amount of downtime. Obviously performance costs money, but in "workstation" class equipment those investments will yield diminishing returns because you're approaching the limits of what technology can deliver.
If your investment lands short of the "sweet spot" range you would be underpaying for equipment, and paying more for your labor to deal with the consequences of that. Landing beyond that range would be overpaying for equipment, in the effort to achieve imperceptible gains in performance at the marginal benefit of reduced labor costs.
You may not be expected to have all the answers, but a good researcher should be familiar enough with these numbers to get a feel for where the "sweet spot" is for your company's specific situation.
Good luck!