What It Actually Costs to Buy VOO from Korea
The expense ratio is the number everyone compares before buying an S&P 500 fund. From a Korean brokerage account, it is also the smallest number in the whole transaction. Buying a US-listed index fund from here costs two things stacked on top of each other: the spread you pay to turn won into dollars, less whatever discount you managed to get on it, and the commission that arrives when the order actually fills. The discount is the part that surprised me. It is not a published price. It depends on which broker you use, on how much sits in your account, and on what time of day you press the button.
The discount is a number you negotiate, not a number you look up
Korean brokers do not advertise an FX fee the way a US broker advertises a commission. They advertise a preferential rate — a discount on the FX spread you pay when your won is exchanged for dollars. And the size of that discount is set per account. Some brokers fix it for everybody. Others decide it based on what you have with them, which means it is something you ask for and agree on, not something printed on a page. I did not know this for a long time. I assumed that the rate I was getting was the rate, in the same way that a price tag is a price tag.
My own two accounts sit on either side of that split. Toss applies a 95% preferential rate to everyone — I do not have to ask, and my balance does not enter into it. Mirae Asset Securities does not hand it over on its own. I had to call and say, more or less, I have this much in the account, can I get a preferential FX rate. As far as I know, brokers other than Toss set the rate account by account like that, rather than posting one rate for everyone.
The same app, the same account, half the discount
Then there is the part that has nothing to do with negotiation. At Toss, that 95% applies when the Korean regular session is open. Convert outside those hours and the discount drops to 50%. Same app, same account, same amount of won going to the same place — and the fee is a different fee because of the clock. Automatic conversion, where you place the order in won and let the broker do the FX for you, is the other way to end up paying more than you meant to. I have never used it.
| How the FX discount works, in my experience | |
|---|---|
| Toss | 95% for everyone, no asking, during the Korean regular session. 50% outside those hours. |
| Mirae Asset Securities | Not automatic. I called and asked, with my account balance as the argument. |
| Others | Per account, as I understand it. |
The time-of-day rule is the one that changed my habits most, because it turns a cost question into a scheduling question. If you are already awake at an hour that suits the US market but sits outside the Korean session, the temptation is to just convert and buy in one motion and go to bed. That is exactly the motion that costs more. The hours themselves have their own post on this blog — Trading US Markets from Seoul.
Then the commission lands on top
The conversion is not the end of it. When the order fills, the trading commission is charged separately, and it comes out of the dollars you just bought. So the amount that actually leaves your account is larger than the amount you were looking at when you decided how much to convert. On paper this is obvious. In practice it is the kind of thing you learn by being slightly short.
I assumed that if the account did not have enough, the order would simply be rejected. It was not. The balance went negative instead, and the broker contacted me with a date by which I had to put the money in. Nothing dramatic happened, but the assumption I had been carrying — that being short is the same as being stopped — was wrong, and it was wrong in the direction where the trade goes through and the shortfall becomes mine to cover.
What I actually do
I convert in advance rather than at the moment of buying, and I do it while the Korean session is open. I have never used automatic conversion. The honest reason is not a strategy: I am the type who really hates paying fees. But the habit does two useful things at once. It keeps the discount at the better end of the range, and it separates the two decisions — how many dollars I want to hold, and what I want to buy with them — so that neither one is being made at two in the morning because the other one needs it now.
What an English-speaking reader may not expect
If you buy a US index fund in the US, the cost of the purchase is close to nothing, and it does not move with what hour you pressed the button or whether you once called your broker to ask for a better rate. That second part is what does not travel. From here, two people can buy the same fund on the same day, in the same amount, through apps that look equally modern, and pay different amounts — because one of them made a phone call and the other did not, or because one of them converted at three in the afternoon and the other at eleven at night. The cost is not a property of the fund. It is a property of how you arranged to get there.
What the exchange rate itself does to your returns once you are holding the fund is a separate question from what it costs to cross over, and it has its own post — The Double Loss Didn’t Happen Today. Buying the same index through a Korea-listed fund is a different route with a different structure altogether, and that one starts elsewhere too — Same Index, Different Tax Bill.
Broker policies described here are as of 2026 and reflect my own accounts. Preferential FX rates, session-based discounts and commission schedules change, and they differ by broker and by account. This is my experience as an individual investor, not advice.