Those are mainland tourist-area "rape me please because I'm unprepared and shopping in this place" prices.
I'd never snorkeled since a couple times when I was a kid and snorkels were straight pipes. They constantly tried to drown you. Not a fun experience. Did not like.
I went in to one of those places described above, didn't know shit but wanted the good stuff, so I took a shot and bought the most expensive mask and snorkel they had, hoping it wouldn't just be overpriced tourist junk. I think it was US Divers brand. I believe the total was something like 90-120 out the door but I bought some other shit and I don't know if that was for the mask and snorkel or if that included the other shit as well. I do clearly remember sorting the mask and snorkel by price and hoping I'd end up with OK stuff that way.
Keep in mind I'm a noob. Holy shit. Easy to use, nearly had to work to get any water in the snorkel. Had several waves go completely over the top of me. Safe as houses. Easy, easy, easy to use. Fantastic experience.
I'm Spock though, so I read the directions. I'd recommend you do so as well if you want to have a great experience. Using the stuff and adjusting it to fit properly isn't race knowledge. It also isn't hard, it just takes attention to detail and a few tries to get it fitting perfectly.
Snorkeling in Hawaii? You're going to have the time of your life. Enjoy!