Here is a shot at a back-of-the-envelope calculation of the sum of fees paid in ...

Here is a shot at a back-of-the-envelope calculation of the sum of fees paid in his first example. I hope I haven't misunderstood.

  var gain = 1.08; var fee = 0.0025; var feeSum = 0; var s = 100000;
  for (var i = 0; i < 35; i++) { s *= (gain - fee); feeSum *= gain; feeSum += s * fee; if ((i + 1) % 5 == 0) console.log('year: ' + (i + 1) + ', saved: ' + s + ', fees: ' + feeSum);}; 

  year: 5, saved: 145240.0514760841, fees: 1823.9448097195082
  year: 10, saved: 210946.72552775557, fees: 5329.071699986484
  year: 15, saved: 306379.13274362596, fees: 11677.706523607205
  year: 20, saved: 444985.2101088223, fees: 22746.568357507604
  year: 25, saved: 646296.7482230144, fees: 41538.4561823357
  year: 30, saved: 938681.7298073637, fees: 72821.71593023202
  year: 35, saved: 1363341.8275688116, fees: 124120.0285076505