Cascade entity reference in a content type
It sounds like you want to try to use Reference Field Option Limit:


  Example 1:
  
  countries and cities Suppose you want to label articles (or
  products, or businesses, etc) by both city and country so both can be
  used for filtering and searching. You could use a hierarchical
  taxonomy with city terms as children of country terms, but that
  doesn't make sense when you come to set up Views filters.
  
  With this module, create two separate taxonomies for country and city
  (or content types, or whatever entity you want to use). Then add a
  reference field so that each city points to its country: eg, the term
  'Paris' has a reference to 'France'.
  
  Then when editing an article, selecting 'France' in the country field
  will cause the city field to update to show only cities in France.


How you denote the different parts based on their price. I dunno. But you can look at this module and if need use it as a starting point to extend or create javascript behaviors or alter sql queries it's using.