For what it's worth, I work in industrial controls. More or less all of the machines we design are one-offs so engineering and labor time dominates the cost of projects vs. materials.
Additionally, unplanned downtime is extremely expensive. If a machine breaks down and a replacement part isn't on the shelf, getting that part fast is much more important than saving a few dollars. Same goes for if we end up with a bunch of guys waiting around for a part to get installed.
I was more referring to issues with shipping and ordering outside of the US. But you are entirely right about them focusing on American measurements, their selection of metric parts is much weaker and more expensive than their customary (main?) Sizes of parts. I do wonder if they are or will be working on improving that any time soon.
Unfortunately I don't see them creating a price filter as they are mainly geared at businesses vs. hobbyists or consumers, where "get it here fast" is more important than saving a few dollars. That being said, I find adding all of the prospective parts to the cart works well for me when I want to compare prices
McMaster-Carr has the best shopping website I've ever seen. The UI is beautifully intuitive; even if I don't know exactly what I need, odds are I can easily find something that will work and they can have it at my doorstep in under 24 hours, no matter how obscure. Even if I don't plan on buying anything, it can be helpful to click through the site just to see what is available. Because most categories of parts have surprisingly well written descriptions and breakdowns, the sire can actually be a good engineering resource.
I've bought from them many times before and have yet to be disappointed with what I got. It is definitely expensive compared to other suppliers or Amazon, etc. But you pay for the convenience.
I hear they aren't very good outside the US though, which is a shame.
Additionally, unplanned downtime is extremely expensive. If a machine breaks down and a replacement part isn't on the shelf, getting that part fast is much more important than saving a few dollars. Same goes for if we end up with a bunch of guys waiting around for a part to get installed.