I assumed that input had to be taken in the way outlined in the 
challenge.
So most of my code is about parsing that to create the required ranges.

=========================

class String
  def better_to_f
    str = match(/\D*([0-9,.]+)/)[1]
    str.gsub!(',','_')
    str.to_f
  end
end

$vendors = <<-STRING
Company A:  $1,000 - $3,000
Company B:  $6,000 - $10,000
Company C:  $500 - $2,500
STRING

vendor_regexp = /(\w.*\w):\s*\$([0-9,.]+) - \$([0-9,.]+)/

$shopper = <<-STRING
Low:   $3,500
High:  $7,000
STRING

require 'yaml'
parsed = YAML.parse($shopper)
low = parsed['Low']   && parsed['Low'].value.better_to_f
high = parsed['High'] && parsed['High'].value.better_to_f

vendors = $vendors.scan(vendor_regexp)
result = []
vendors.each do |name, min, max|
  min = min.better_to_f
  max = max.better_to_f

  if low && low >  max
    next
  elsif high && high < min
    next
  else
    result << name
  end
end
-- 
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