I like using .toJSON in the browser console to see what records look like

require(["N/record"], function(record) {
  var item = record.load({ type: "inventoryitem", id: 'whatever id' });
  var line = 0;
  console.log(
    item
      .getSublistSubrecord({
        sublistId: "itemvendor",
        fieldId: "itemvendorprice",
        line: line
      })
      .toJSON()
  );
});