Hi @frommtron,
Yes it’s definitely possible to get under $100 / person at Gwang Yang BBQ and Park’s. We just did it over the course of… 8 visits? Not once did we go over $100 / person. 
Also Gwang Yang has a far more extensive additional menu that might fit Vegetarians. Some examples include:
- Kimchi Jeon (Kimchi Korean Pancake)
- YaChae Dol-Sot Bibimbap - Stone Pot Rice Bowl (with @J_L’s beloved socarrat crispy rice at the bottom of each bowl).
- Doen Jang Jjigae - Korean Soybean Paste Stew with Tofu and Vegetables (this was quite tasty for a non-specialist).
- Nurungji - Korean Roasted Rice Soup with Soybean Paste Stew
If they’re OK with seafood (pescatarian), there’s even more options.
Also Gwang Yang BBQ has more Private Rooms that you can book than Park’s.
That being said, Park’s will always have a special place in my heart (it was my favorite KBBQ for years), but Gwang Yang is just a touch better (for us) for the meats / flavors.
Also Park’s BBQ has one of the best Banchan spreads in L.A. (90% of those complimentary side dishes are Vegetarian, and bottomless), so that will delight your Vegetarian friends as well. 
Enjoy!