Here is what I believe is the best current detailed binocular review.
This is another very useful review of binoculars by the Cornell Lab of Ornithology. It’s a bit dated, from 2013.
I recommend that you don’t look at most other binocular reviews. They’re often not current, or not thorough, or they’re an ad trying to sell you the models they sell. (And some of them don’t even know anything about binoculars!)
You can frequently get excellent deals on eBay. I’ve bought three binoculars that way, generally saving $100 to $200 on pricey binoculars. (I only buy from sellers with excellent reviews; with a favorable return policy; and where the binoculars are in new or nearly new condition, for example, a retailer who can’t sell them as new, because the box had been opened.) ‘Open box’ and ‘refurbished’ binoculars from a reputable dealer often have very good prices.
My regular birding binoculars are Nikon Monarch 7, 8X42. Monarch 5 are similar in quality, but cost less. I did own $2000 binoculars (Swarovski), and they were stolen in Costa Rica. That was rather a devastating loss, so I decided not to spend that kind of money again on binoculars.
There are binoculars that might cost twice the price that are of the same quality. You can spend $2,000 more, and get binoculars that are 20% better, which might not be the best use for $2,000. At the very least, look through $2,000 binoculars side-by-side with $400 binoculars, and then you can judge for yourself.
If you’re serious about enjoying birds, cheap binoculars will, over time, strain your eyes more and lose some of their lens coating, which diminishes clarity and image brightness. If cost is a major issue, at least plan to spend in the $200-plus range. (I recommend that you read the reviews, and decide the tradeoff you’re comfortable with.)
There are lots of choices. I recommend that beginner birders get 8X, rather than 10X because you get a wider field of view which makes finding the bird easier.
If you hike and/or travel often, I strongly recommend considering the weight of the binoculars.
There are lots of other things to consider, for example, “eye relief” if you wear glasses and have an astigmatism; and objective lens diameter (e.g., 32, 42, etc.).