This is poor bonus in that case because iTunes gift cards are regularly on sale for 15% off so you’re better off waiting for that unless you need the funds ASAP.
That’s right. It’s only a 9% discount ([1 – $100/$110] × 100% = 9%). The best I’ve seen—though rarely, only—for iTunes gift cards purchased online is $100 value for $80 outlay, a 20% discount.