You can get an all-you-can-eat course here starting from ¥2,800. The 100-minute course includes beef, pork, vegetables, Chinese noodles, and udon noodles. If you add the all-you-can-drink order, it'll be an extra ¥1,500.
Below is the Kabukicho location but there are many other locations across Tokyo.
Nabe-zo also has a dinner all-you-can-eat course that is just ¥2,800 for 100 minutes. The quality is pretty good too. They use domestic vegetables and no artificial flavours are added to the broth.
The vegetables are self-served.
The restaurant has many locations across Tokyo, including a popular one near Shinjuku's East Exit.
This place is really cheap! The standard all-you-can-eat course is just ¥1,899 for 90 minutes. You can also enjoy a course that includes domestic beef and porc for ¥2,999. This is the most expensive option but it is still very reasonable.
Sainoan is on the 9th floor of the Lumine department store in Ikebukuro.
On-Yasai is the biggest chain restaurant serving shabu shabu in Japan. They have over 380 branches throughout Japan and becoming more and more popular, for the delicious, reasonably priced all-you-can-eat shabu shabu! The cheapest all-you-can-eat course starts at ¥2,780.
Below are two popular locations in Tokyo but they are many others.
Bone 梵 渋谷店
Bone is a cheap izakaya in Shibuya that offers an all-you-can-eat nabe (hot pot) and shabu shabu all-you-can-eat options. Being a tavern, it has a really good drink selection that includes beer, wine, shochu, sake, whiskey and more!
Another thing that is popular at the moment is this cheese dakgalbi which is also all-you-can-eat!