Thank you vs Arigato

The word 'thank' derives ultimately from the Proto Indo European word 'teng/tong'- for thinking/feeling.

'Thank is to Think as Song is to Sing.' 

Thus, thankfulness is a function of the thanker's level of sentience and capacity for refined sentiment and thus thanks offered can be ranked qualitatively on the basis of the thanker's status as well as the amount of effort, talent and creativity the thanker puts into formulating her thanks.
Prayer is a form of thanks and as St. Augustine of Hippo is often quoted as having said “He who sings, prays twice.”  The Latin cited for this is “Qui bene cantat bis orat” or “He who sings well prays twice”.
This attribution probably derives from the following passage-

Qui enim cantat laudem, non solum laudat, sed etiam hilariter laudat; qui cantat laudem, non solum cantat, sed et amat eum quem cantat. In laude confitentis est praedicatio, in cantico amantis affectio…For he who sings praise, does not only praise, but also praises joyfully; he who sings praise, not only sings, but also loves Him whom he is singing about/to/for. There is a praise-filled public proclamation (praedicatio) in the praise of someone who is confessing/acknowledging (God), in the song of the lover (there is) love.

The literal meaning of Arigato, however, is 'It is difficult to exist' and arises as something objective which the one being thanked has recognized as requiring some altruistic action on their own part. Thus, qualitatively,  thanks rendered can't be graded on the basis of the level of sentience or refinement of sentiment or degree of affection possessed by the thanker but, rather, it is the one being thanked who determines the quantum of thanks appropriate to his act of benevolence which is itself interpreted as a 'concession' (Suijo) to objectively discerned neediness, the transparent difficulty faced in simply carrying on existence, of the one who ought to render thanks and 'repay virtue' (Hotoku) but on whose behalf the collective is equally obligated and empowered to act.

Thus to say 'thank you'- not that us low class desi types ever say please or thank you- is to affirm one's own worth and status and creative talent. It is more than to sing for your supper. Rather it is to drunkenly grab the karaoke mike at the bat mitzvah you've thuggishly gate crashed and, quite madly, decided is actually a surprise birthday party for yourself.  What? Don't tell me you have no memory of doing any such thing. You are ten times worse than me. Fact is us desis can't hold our liquor. My old drinking pal, M.S Subbalaxmi, once got high on peppermint Schnapps at the Indian Consulate in New York and barged into the General Assembly and grabbed the mike from Gowdamma Iyer, first Tambram Prime Minister of Israel, and sang Nole Kidre in Raag Hindolam- thus deeply affronting  Gemal Abdul Nasser who had been practicing that same item all week. This led to the Yom Kippur War.

I am not guilty in any way. All I said to her was 'Arre gaa to'. That she chose Raag Hindolam is the fault of that Schopenhauerian Will which always works in such a way that what is most difficult is bare existence.