Launch HN: Double (YC W24) – Index Investing with 0% Expense Ratios

Re:Launch HN: Double (YC W24) – Index Investing with 0% Expe... by darkerside on Wednesday December 11, 2024 @07:04AM (#42386947)

There's also time value of money. Paying upfront like this means that money can't be invested (by you), and you lose out on the money plus the return.

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Re:Launch HN: Double (YC W24) – Index Investing with 0% Expe... by dlubarov on Wednesday December 11, 2024 @01:05PM (#42390741)

Wouldn't that be for fixed-dollar fees? I think here all the costs we're talking about are percentages.

I.e. ignoring taxes, the amount I theoretically expect to exit with should look like

    entry_cost * (return_rate * fee_rate)^T * exit_cost

Where return_rate might look like ~1.1, fee_rate might look like 0.9983 (17 bps), and entry_cost and exit_cost might look like half_spread/price (under some assumptions...).

So I think this comes down to whether T is large enough for that exponentiation to dominate the half-spreads.

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