He's bought a big TV at vast expense so that everyone can see properly.

他花了很多钱买了台大电视，这样人人都可以看清楚了。

《柯林斯英汉双解大词典》

He has bought a specially big TV at vast expense so that everyone can see it properly.

他花了很多钱买了一个特别的电视，为了能让大家都看清楚。

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Moving and equipping the house has been a vast expense and, after splitting our savings, X and I haven't talked about money at all.

搬家和买家具是一笔很大的费用，而在我们的储蓄分开后，X和我根本就没有谈过钱这方面的事情。

youdao

In the past, France has seen a series of state-led bailouts, at vast expense to tax payers.

ECONOMIST: Going bust in Europe

There've been any number of reports telling us that services aren't set up right, aren't configured in the best way possible, any number of clinicians and health economists accusing successive Welsh governments of revamping at vast expense but to no real avail.

BBC: In the red, in the firing line

Companies obliged, at vast expense.

ECONOMIST: Who��s to pay for Y2K?