Can anyone recommend a good pair of opera glasses for a decent price? When I look on Amazon, there are just so many, and I don't know what to even look for in a good pair.
Rather than doing a search for 'opera glasses' on Amazon, do a search for 'portable binoculars.' The quality of the image will be much better with those, and they have many options for around $20. Reading the reviews will give you a better idea of which ones are good, but I'd assume that any of them would be great for the theatre.
If it's not too inconvenient, I would suggest finding a store that will let you try them in-store before you buy. I found a pair that looked like the perfect type for me online, but when I sought them out in a physical store the 'view' through them wasn't so great. I ended up choosing another pair that had initially seemed unsuitable based on the online specifications.
I have a Bushnell pair 8x21. I bought them on Amazon and they work for me. Theater, opera, whatever. Though if you really want a close view at the opera, you might go for a higher magnification.