Does it make sense to use miles cards if you are not intending to take Business Class flights? This is something you can decide by comparing the miles required against the cash you’d have to pay for ticket prices in Economy Class.
Generally, the miles required for a particular flight is fixed while ticket prices can vary depending on the dates you travel in. This means that when ticket prices are high, redeeming a flight with miles makes more sense since you are offsetting more spend using your miles.
Looking at a real example
Let’s start with a short regional trip to Bangkok on Singapore Airlines.
Looking at the available flights over the next few months, the cheapest return trip I’ve found in Economy Class is around S$311. The miles required for this return trip is 26,000 miles with around S$114 of taxes.
Someone using a 4 miles per dollar card will need S$6,500 spend to collect the 26,000...