To prevent recommendations for products priced under $15 in a Marketing Cloud Personalization recipe, marketers should utilize the Exclusion ingredient. This powerful feature allows for fine-grained control over recommendations by specifying criteria that disqualify certain items from being suggested.  

Here's how the Exclusion ingredient works:

Defining exclusion criteria: Within the recipe, marketers can define specific criteria that exclude products from the recommendation set. In this case, the exclusion criterion would be "price less than $15."

Filtering recommendations: When the recipe generates recommendations, the Exclusion ingredient filters out any products that meet the defined criteria. This ensures that only products priced $15 or higher are included in the final recommendations.

Flexibility: Exclusions can be based on various product attributes or dimensions, providing flexibility in tailoring recommendations. This allows marketers to create highly targeted recommendations that align with campaign goals and customer preferences.