I also buy second-hand whenever possible, and try to fix things instead of replace them, and for the stuff I’m buying it’s usually more expensive, not less. Especially when big stores offer free delivery on just about everything while your average ebay user obviously doesn’t.
Recent example: I got a shoulder strap for a clutch bag and the clasp on the strap broke. It was only missing a tiny spring, so I found a tiny spring online and repaired it. The strap cost £5. The spring to fix it cost £6 including postage. But it worked!