To ignore taxes and to assume that you're only holding an S&P500 index, it's 2yearsfee (let's say $10 * 2 * 20==$400). Kind of insignificant.

To not ignore taxes though it becomes more clear. If you literally sell every May, you're never holding for more than a year. In the US at least you're always paying short term capitol gains. This is the real killer here.

Given it's an analysis of the S&P500 you just buy/sell SPY and follow the index. Not that I recommend that, for reasons other people here have pointed out.