When you buy an ETF, the number on the factsheet is only the beginning. Domicile determines withholding tax on dividends. Exchange determines spread and liquidity. Currency determines your FX conversion cost. Together, these three variables can treble the real cost of ownership.
Domicile: the silent cost
Ireland has a double-taxation treaty with the US that reduces withholding on US dividends from 30% to 15%. Luxembourg does not. For a global equity fund yielding 2%, that 15% gap is worth 0.30% per year in drag — more than the stated fund fee on many trackers.
Exchange liquidity matters
An ETF with tight spreads on Xetra can cost you 0.02% to trade. The same ETF on a smaller exchange with wider spreads can cost 0.15%. Over monthly contributions, that difference compounds.
The real ranking
For a UK-based ETF investor, the cheapest route is typically: Irish-domiciled + accumulating + EUR share class on Xetra or Euronext Amsterdam. The most expensive: German-domiciled + distributing + GBP share class on a low-liquidity exchange.