Here is a summary of the earphones I’ve purchased recently from eBay. All of them are relatively cheap in price ($10 to $20) and have good sound quality.
Good sound quality. Superb bass.
Price: about $10.
Good sound quality.
Price: $6 – $10
Good highs and mids. Good sound isolation.
Price: less than $20
Good sound quality.
Price: about $10
Don’t go for earphones that are priced for less than $5. A reasonable buyer won’t spend hundreds of dollars on earphones either.