What’s a good English expression for the Chinese idiom "buying horse bones with much gold" (千金买马骨)?

Solution 1:

For the story’s plot about showing just a hint to elicit interest, consider: “Sell the sizzle, not the steak”.

Anyway you say it, it all comes down to the simple fact that people “Buy on Emotion and Justify Their Purchases Using Facts“. - Simple Small Business

For your interpretation regarding focusing on the fundamentals, consider “back to basics”:

back to basics Returning to the fundamental aspects of something. Since you're struggling to play chords, let's get back to basics and look at the notes on the scale. - The Free Dictionary, citing Farlex Dictionary of Idioms