John bought chairs for his office. The original price for the chairs was $45 EACH, but they had been marked down by 30 percent. How much did John pay for 10 chairs?

The chairs had been marked down by 30 percent, so the new price for each chair is 45 - (30/100) * 45 = $31.50.

John bought 10 chairs, so he paid a total of 10 * $31.50 = $<<10*31.50=315>>315. Answer: \boxed{315}.