Well, let's assume a few things to place this into perspective:
First, besides the numbers, lower taxes, accountability of the use of money and less intervention in the lives of American citizens by the government is a good thing. Taxation is necessary for a functioning nation, enforcing less taxes is even better in this function.
Now, let's forget the old models of growth. If Trump can hit 2%+ annually for his term, that is a minimum of 8% growth on this economy With this growth is higher revenue and less people on welfare, helping both sides of the ledger. As it were, he could hit 3.5% growth this year and maybe even 4% next year, who knows? So 12-14% for these four years is not out of the question, a major estimation that most economists don't use. If he beats these results, the tax cut will be a blip.
Consider the $4T that might be injected back into the economy, taxed at 21% or whatever that number might be
Consider the expansion of businesses, buy backs of shares (which when sold by investors, is, you guess it, taxed).
All of this would add revenue. Most important though will be jobs during the expansion. Increasing revenue sources while decreasing expenses in the ledger.
All in all, these cuts are valid and if he succeeds he will make everyone look foolish, if he hasn't already. What will be key going forward is how he addresses abuses of trade from China, Mexico and Canada. If he decides that trade deficits are unacceptable, abuses too great and demands tariffs, that will be trillions back into the U.S over 4 years. Don't worry, it won't hurt the consumer much, the companies will have to accept lower profits, or face further competition if they price themselves too high.
God Bless America! Get 'er done Trump!