As someone who was born and raised in Japan, I can safely assure you that Raku is absolutely the most authentic, the best Japanese restaurant in Las Vegas.
Before moving to Vegas, I had lived for 8 years in San Francisco Bay Area, and there were great Japanese restaurants, but few match Raku.
Although on the high end, the prices aren't crazy expensive either, I'd say it's reasonable for the quality.
I'm very surprised that most of Japanese restaurants on the Strip are mere gewgaws, full of upscale looking gimmicks, but I won't complain because we have Raku!