If that $1300 includes three or more coats of the finish, the amount is a little high. Water based finishes are from 1&1/2 to 2 times more expensive than oil based finishes. The major esthetic difference is the added color. Oil based finishes add an amber color, which is usually pleasing. Water based finishes add no or very little color, which can sometimes look drab or washed out. Oil based finishes used to be tougher and longer lasting. Research and development of newer water based formulas bring that variety closer to the performance of oil based. And, finally, water based floor finishes take much less application/drying time, sometimes 2 days and have much less odor until dry.

You are correct in that using a drum sander is not at all DIY friendly. But it's the only way to correctly sand a floor down to smooth and ready to finish. You will take years trying to do the same thing with an orbital. The rental rate for the sander is going to be more than hiring the right pro with the right equipment.

Engineered wood flooring is going to be dried close to that range regardless of where it's produced. After installation it should be allowed to acclimate to your conditions. My two favorite mills went under during the pandemic. The one I've been buying from lately is Maxwell, based in NW Arkansas. We're just finishing up an 850' job of plain sawn 6" White Oak and it looks great. Being in CO, you may have a completely different set of viable suppliers than I have in southeast Florida.

I recently installed my own engineered european oak, and as a hobby woodworker I felt comfortable in selecting and installing the wood. But your question can be a bit open ended depending on what you're looking for in the higher price ranges. There are a couple things to be aware of. Firstly, as @DeWayne said your installer may already have a source or sources they're used to working with. They may be unwilling to go outside their usual sources (and understandably so). So you may wish to speak with them first. If you select your own floor and something goes wrong with the order or install the fault may land on you if you go outside their recommendations. If you are free to chose your own, the first thing I would caution against is going with a big box store or chain. I looked at samples from places like Floor and Decor and Lumber Liquidators just out of interest. What I found was that their highest end products looked suitable but were no longer any cheaper in that range relative to direct from mills, so at that point you're better off just working with a small supplier. Plus their wear layers then to be on the very thin side. Ideally you want a wear layer of at least 3mm to have the depth of real hardwood. Even if you don't ever refinish, a paper thin wear layer means any slight damage to the floor exposes the plywood underneath. In all my searching, I can't think of any I saw in the $20 a sqft range for just the bare floor. The only one I know in that range is in the house of a friend of mine who is a custom home builder and used hand scrapped prefinished engineered hickory at the cost of $20 a sqft. If you order directly from a mill you can find nice flooring in the $6-12 a sqft range. I ended up using flooring from Hurst Hardwoods, 5/8" thick by 10 1/4" european oak and was really happy with it. If I didn't go with them, I would have ended up choosing Sawyer Mason, which isn't available in all parts of the country but since you said you're also in the Northeast you may find a local dealer. Theirs was like walking on a piece of furniture, and still in the $9-12 a sqft range.