Lasaña (or Lasagna as we American's spell it) in general in Japan is not very good. They use the wrong cheese, they add things that shouldn't be added. Overall I've always found it quite disgusting. Lasaña is my most favorite dish. Even making it in Japan is hard. To make it correctly you have to make the sauce from scratch because most of the red sauces in the stores don't taste very good. The Ricotta is expensive. 250g for ¥1000 and you need 2 containers to make an 30cm x 30cm pan of Lasaña. Basically if you are going to make Lasaña it's going to cost you about ¥3500-¥5000.
Some things that bring the cost down. Costco sells Ricotta ¥800 for 16oz(I think it's 16) container which is more than enough for Lasaña, and the shredded mozzarella can be bought in a big bag for ¥1000. You can also get a decent Marinara sauce there. Or if you are adventurous you can make the Ricotta from scratch for about ¥500 with Milk and Lemon Juice/Vinegar but you also need cheesecloth, and a candy thermometer.