function downloadAllGmailPictures() {
  // Get all Gmail messages.
  var messages = GmailApp.getInboxThreads();

  // Create a folder in Google Drive to store the pictures.
  var folder = DriveApp.createFolder("Gmail Pictures");

  // Iterate over all messages and download any attached pictures.
  for (var i = 0; i < messages.length; i++) {
    var message = messages[i];
    var attachments = message.getAttachments();

    for (var j = 0; j < attachments.length; j++) {
      var attachment = attachments[j];

      // Only download pictures.
      if (attachment.getContentType().indexOf("image/") == 0) {
        // Save the picture to Google Drive.
        var file = folder.createFile(attachment.getName(), attachment.getBytes());
      }
    }
  }
}

With no page or info on how much more that $5 it might cost.