The sizes of Parsoid- and non-Parsoid-generated (very nearly almost all Cite-generated) element IDs on https://en.wikipedia.org/api/rest_v1/page/html/Barack_Obama.

Barack_Obama.js

// $ curl -so /dev/null https://en.wikipedia.org/api/rest_v1/page/html/Barack_Obama -w '%{size_download}'
var TOTAL_BYTES = 1582727;

function total_bytes_for_ids(ids) {
  return ids.reduce(
    // 5 additional bytes for the "id=''" string
    (acc, id) => acc + id.length + 5,
    0
  );
}

var ids = Array.from(document.querySelectorAll('[id]')).map(el => el.id);
var ids_bytes = total_bytes_for_ids(ids);
console.log(ids_bytes);

var non_parsoid_ids = ids.filter(
  // Parsoid IDs are prefixed with "mw" but some reference IDs are prefixed with "mw-".
  id => (id[0] !== 'm' && mw[1] !== 'w') || (id[0] === 'm' && id[1] === 'w' && id[2] === '-')
);
var non_parsoid_ids_bytes = total_bytes_for_ids(non_parsoid_ids);
console.log(non_parsoid_ids_bytes);

console.log(ids_bytes / TOTAL_BYTES);
console.log(non_parsoid_ids_bytes / TOTAL_BYTES);

OUTPUT

88845
34107
0.05613412799554187
0.021549515488141668