東京リージョンのVPC内に t1.micro のスポットリクエストを送るときに使う
それっぽい値段を出す

AZ片側だけで判定(ap-northeast-1a)
立ち上げるマシンはLinux

Ruby2.0.0-p247
aws-sdk 1.22.0

require "aws-sdk"

AWS.config(
  :access_key_id     => "access_key_id",
  :secret_access_key => "secret_access_key",
  :region            => "ap-northeast-1"
)

def soreppoi_price
  ec2 = AWS::EC2.new
  options = {
    :instance_types    => ["t1.micro"],
    :availability_zone => "ap-northeast-1a",
    :start_time        => (Time.now - 60 * 60 * 24).iso8601,
    :filters           => [
      {
        :name   => "product-description",
        :values => ["Linux/UNIX (Amazon VPC)"],
      }
    ],
  }
  resp = ec2.client.describe_spot_price_history(options)
  resp[:spot_price_history_set].each {|history|
    return history[:spot_price].to_f + 0.005
  }
end

puts soreppoi_price

参考にしたもの
http://itsneatlife.blogspot.jp/2013/08/aws-sdk-rubyspot-instancepricing-history.html
http://docs.aws.amazon.com/AWSRubySDK/latest/AWS/EC2/Client/V20131001.html#describe_spot_price_history-instance_method
http://docs.aws.amazon.com/AWSEC2/latest/APIReference/ApiReference-query-DescribeSpotPriceHistory.html (Supported Filters)