He held this opinion for far too long, and it would prove very costly.

The title challenge proved costly, and after a financial down most of the star players left.

The campaign is proving a lot more costly than anticipated.

In some way, his examination had proved costly to him.

So this year's hard line could prove costly in the future.

In addition, keeping the bank on life support was proving costly.

Even getting horses to the island proved more costly than expected.

They're not going to prove costly at all, are they?

But the move could prove costly in the long run for the bank.

In any case, such legal victories could prove very costly.