Allowing the searching and purchase of used equipment would also help those facilities running on a shoestring budget.
How to start a lab when funds are tight: https://www.nature.com/articles/d41586-018-05655-3
How to start a lab when funds are tight: https://www.nature.com/articles/d41586-018-05655-3
We have a catalogue of approved suppliers who are easy to order from (semi-automated system). The usual suspects like Farnell/Digikey, Thorlabs/Edmund Optics are in there. Most universities have a "credit card guy" who will order things from other places, e.g. if you need a random part from an online retailer or even eBay.
Some suppliers have special relationships, e.g. we get hefty corporate discount on certain IT brands in exchange for exclusivity. This means you have to really argue why you want a non-standard laptop. I've not come up against this for consumables, but I imagine it's fairly common in bio/chem.
There are other cases which are problematic (1) big orders need extensive approval, multiple quotes, etc (2) stores which are not in the system and don't accept credit cards. Adding a supplier at any university is often tedious paperwork for everyone involved and neither the finance department nor the retailer like doing it.
The point here is that it's great to be able to find cheap supplies, but sometimes you can't make that choice. I've had to buy expensive (but admittedly reliable) optics from Edmund simply because a cheaper store wouldn't fill out the paperwork. These sites are great in general, e.g. Octopart for electronics.
EDIT: (meant to reply to this one)