When I purchased my mill about 10 years ago, I ordered a set of Chinese TiN coated 4-flute end mills with with lots of other accessories from Grizzly. Here it is 10 years later and they are still servicable and cut as well as I remember them cutting when they were new. One of them chipped when I dropped it.
They don't get heavy use. I work mostly with aluminum, but have done a few pieces in steel.
When I purchased them I made a judgement call and got 4-flute end mills, because I figured they'd work on aluminum but I also wanted to be able to work with steel.
A couple weeks ago, I noticed a set of 10 2-flute TiN coated end mills on sale for about $40 at Enco with free shipping, so I got a set based on my experience with the other set. I couldn't be more pleased with them. They do an even better job on aluminum. I've milled two or three pieces with them and the cuts are near mirror smooth.
I was also wondering why it would be advisable to spend 3-4 times as much for end mills, given my experience with the ones I've been using. I have a few US made end mills, even a couple of solid carbide, but I can't tell any difference in their performance.
I'm guessing the difference could be that I'm a one man shop and the mill is just one of many tools I use in any project, so it doesn't run all day long, nor do I do production runs.
I like fine tools and I have quite a few, but some of my tools were required for a specific and rare need, and are just serviceable. But, they earn their keep. Sometimes, quantity has a quality all its own.