People really are strange sometimes! Disgusting? disposables not that expensive? What the? I don't know anyone that weird!
I am a total cheapskate when it comes to nappies, and proud of it. Just tell those friends of yours that you will enjoy spending your money on more enjoyable things for bubs than bum covers.
Why does it matter to them anyway? Do what feels right to you and don't worry about the opinions of others. Start thickening that skin now because there will be plenty more occasions when you will need to brush off ignorant comments from people who think they know best.