(maxim) a mere "thank you" is an insufficient response to a huge favor / (expression of gratitude) words cannot express my appreciation for what you have done
意思意思
yì sī yì sī
to do a little something as a token of one's appreciation / to express one's gratitude or esteem by treating sb to a meal or presenting a gift
叨扰
tāo rǎo
to bother / to trouble / (polite expression of appreciation for time taken to hear, help or host the speaker) sorry to have bothered you / thank you for your time
惜才
xī cái
to have an appreciation for talent in another person