We're going to trade up to a larger house.

我们打算卖掉房子，再买一座大点的。

Let's trade up and get a better car.

我们折价换购一辆更好的车吧。

Many sold out to trade up, getting homes with running water and electricity.

他们卖掉了许多洞穴，以便筹钱为家里装设水电。

There are people who need to 'trade up' to a new car every three to five years.

有些人每隔三五年就要换部新车。

One recent trend is for residents to trade up to bigger, newly built apartments.

最近的一个趋势是，居民们开始购买更大的新建公寓。