I'll say it again for the millionth time. Buying the translation book DOES NOT HELP THE SENSEI. The writer was paid by original publisher full stop. Then Japanese publisher sells the rights for one sum to other publishers. The other publishers then make money selling however many copies to book stores, Amazon, etc. There is NO amount per book going back to the Japanese publisher, much less the writer/artist.
If you want to support the writer, find their patreon, and donate directly. If patreon does what it should, then one day we'll be able to cut the publisher out of the mix completely, and the author will be paid directly by the readers. So, um, FUCK THE PUBLISHER. Do not buy translations. Support the author in other ways.