Keeping costs low is a key battle for investors. At least once a year you should take a look at how to whittle away some costs, whether it is by introducing cheaper core holdings or transferring your investments to an investment platform with lower fees. You may be able to benefit from a price war between providers of tracker funds and exchange traded funds (ETFs) over the past year. In last week's ETF portfolios, we saw expert David Liddell swapping iShares MSCI Europe ex-UK UCITS ETF (IEUX) with a total expense ratio (TER) of 0.4 per cent for Vanguard FTSE Developed Europe ex UK UCITS ETF (VERX) with a TER of 0.12 per cent.