It's probably better not to say something (lie by omission?) than lie outright - not about anything important though! I've sold things that are brand new basically because they were presents that I loathed, but I could hardly say it looks tacky and cheap on the ad, so better not to say why it's still got tags on....
People have different needs and tastes so the pushachair might be crap for you but ideal for someone else.
Don't confuse the customers!