"That project's budget is too low" should not be marked wrong. It's more accurate to the original chinese since it's expressing ownership in the same way
Accepted now 5.9.2020.
why is it not 太低了？
Also correct, but unnecessary in this sentence, especially as it makes the statement sound less official or "business-speak" and more casual.
budgets can be big and small as well as high and low. 'The budget for that project is too small' should be accepted