I've been twice in a year, unfortunately.
The first time my 17 lb dog was attacked, bitten & viciously shaken by a large dog. She had blood in her eye and teeth marks in her face. She was seen right away and we were told she was lucky it hadn't been a couple of cm in any other direction or she would have lost at least an eye. I opted for antibiotics in case she got an infection in her eye (you can't buy another one of those!) but declined other treatments - received no flack.
The second time she ingested 1/4 lb of fudge - they induced vomiting, and allowed me to take her home with constant monitoring, with the recommendation (that I followed) of subcutaneous IV to deter issues with her liver.
Neither time was I asked to pony up money in advance - maybe for the more acute cases?? It's pricey, but any emergency vet will be. They're understanding, kind and always give me options without making judgment.
I'll be back (if I have to).