Why is so much tax taken out of my bonus, and do I get some of it back?

Bonuses are 'supplemental wages,' and the IRS lets employers withhold federal tax on them at a flat percentage (commonly 22% for amounts up to a threshold, higher above it) rather than using your normal paycheck tables. If your actual marginal rate is lower than that flat withholding, the excess is not lost; it is reconciled when you file, effectively increasing your refund or lowering your balance due. If your marginal rate is higher, you may still owe more. The bonus is not taxed at a special penalty rate; it is ordinary income like any other. If large bonuses routinely inflate your refund, adjust your regular W-4 so your overall withholding evens out.