Yes, it’s technically cheaper but the Basic Economy ticket isn’t worth the savings – and probably won’t save you anything in the long run, especially if you happen to travel with luggage, according to the Wall Street Journal.
The Basic Economy Fare as sold by Delta, United and American, is about $30-50 less than “Standard” fare but lots of downsides including:
On all three airlines: no seat assignment until after check-in or at the gate. Worse, you’re the most vulnerable to losing your seat if the flight is oversold (aka “involuntary denied boarding” or “getting bumped.”) If you’re traveling with a group or family, there’s no hope of sitting together.
United and American: You can’t put anything in the overhead bin without a $25 charge each way (so there goes your modest savings from getting the Economy fare.); You also board in the last group, further reducing your chances of finding bin space.
Delta gives you overhead space but again, you board last.
United: you can’t even check-in online unless you’re checking luggage (i.e. paying $25). you have to check in at the airport. And, oh, no frequent flier miles. (American and Delta let you have miles.)