Which parts to skimp on when buying a server? [closed]

I'm purchasing a reasonably high-end server for our lab, and I'm wondering what parts I should simply leave as the default and upgrade after-sale.

At least in Desktop PCs, the conventional wisdom is that it's cheaper, for example, to buy RAM from "the internet" rather than Dell or HP.

Traditionally nothing, unless you enjoy trying to troubleshoot hardware ^^

Doing enthusiast PCs is one thing, and definitely fun and rewarding as well - upgrading with parts from all over the world getting it to work in unison.

A single server then, one could find that fun to mess around with as well or as a learning experience.

For a bunch of servers? No way. You pay the manufacturer for parts that are thoroughly tested with each other to be sure there's no hidden problems or compatibility problems lurking in the shadows - stealing your valuable time.

If there's something I'd skimp on it would be hard disks for large, slow storage devices that will be used for archival purposes perhaps. Then it might make sense to get cheaper drives from a 3rd party just because you're getting a lot of them and there's a lot of redundancy. But even that could prove challenging, according to the SO server blog posts ^^

(But as it's only a single server for a lab, which doesn't sound all that critical, it's more of a policy and/or philosophical question. I always went a bit custom the first years, only to realize it wasn't worth the time when things went wrong. I've tried skimping on all sorts of parts. Memory and disks are obvious, but these days I'd only buy original parts meant for the specific server revision. I've tried upgrading single-cpu dual-socket servers with the correct cpu bought from a local store and a fitting heat sink, only to miss out on the needed voltage regulators whose extra cost completely swallowed the savings of the cheaper cpu. I've tried adding big name raid cards which at times either clashed with the built-in mobo-controller or just had problems routing cables when there were official options available for not much additional cost...)

Rack rails. Never ever ever buy rails from the server manufacturer. There is an entire industry devoted to third party rack rails, and their products are better and as much as 80% less expensive.

External stuff. Don't buy the keyboard, mouse, screen, net switches, printers, USB memory etc. All that stuff they try to shove you in, when you're buying server. They'll re-branded stuff, that you can by in any store for half a price, and they don't really heave any effect on performance nor stability of the server. If you need the server, buy only the server.

Presuming that your "lab" isn't a quasi-data center, skimp on the lights out features (HP iLo, Dell DRAC, IBM RSA), don't buy redundant power supplies or SAS disk.

Another way to save money is to buy promotional "Express" configurations that are ready to ship, buy refurbished or whatever your local reseller has lying about.