OP, the price point of $600 definitely limits your options, but there are plenty of reasonably good scopes out there, and the Trijicon's one of the best at that price. It's great.
As you go up in price with optics, you definitely do get big bumps in quality, and you probably need to get over $1500 before you start seeing significantly diminishing returns with increased costs. As in, you don't get double the optical "clarity", or won't see twice as long after sundown, by doubling the price point. You're still getting increased capabilities, but the advantages get smaller and smaller, while the costs definitely don't go up in smaller and smaller increments.
Bear in mind, that's with the quality of the actual unit. There's a different inflection point for diminishing returns on what you personally can get out of a scope, or need out of a scope - and what your rifle is actually capable of is also an important factor to include.
As to what you do get as price goes up is better glass; coatings that help with light transmission and better clarity of the different wavelengths coming in; better reliability and durability of the overall system; better precision and repeatability of the erector; higher quality materials in various places...the list goes on. And generally speaking, the "more" you want of any of these things, the heavier the scope gets.
A couple of decades ago, a pretty good rule of thumb was to plan on spending about as much on your glass as you did on your rifle - they'd match capability and need pretty closely. These days, when it seems even some of the entry level guns can get MOA accuracy, it seems for many they get a better match between gun and optic by spending about 2x the cost of the rifle on the scope...it's a very rough and unscientific guideline, but again, it seems to track pretty well in matching the capabilities of the gun and how it may be used.
Again, the Creedo's a solid choice in that price point - you can take plenty of peace of mind in that selection.
