I love to eat massive quantities of Sashimi, but it's usually so overpriced in most Japanese Restaurants - What's the best deal on a Sashimi plate in LA metro where I will not have to visit the hospital afterwards! I thinking a fairly filling plate for under $15.
Get the sashimi lunch special at Sushi Gen (in the Little Honda Plaza, 2nd and Alameda near Little Tokyo.) It has excellent cuts of fish (including toro, yellowtail, spicy tuna, salmon, albacore, and other cuts) with lots of soup and sides for $13. Either go early (right at 11:00), or late (after 1:30) or be prepared to wait for a long time. Can't get the specials at the sushi bar.
The sashimi special at Sushi Go 55 on the 3rd floor of a mall on 3rd and Alameda is also very good although not quite as good as Sushi Gen. But, there's no wait, or a much shorter one.
Another very inexpensive way to get lots of good sashimi is to go to Safe n Save, a Japanese market on Sawtelle next to Hide, and just buy it at their fish counter.
You should try the Lighthouse in Santa Monica off of 3rd Street Promenade and Arizona. They are an all-you-can-eat Japanese buffet for around $20 for dinner. They have all-you-can-eat sashimi at night, and it's pretty decent quality. One of the best Japanese buffets around.