1,你的回答不对,有罗嗦和Chinglish的毛病,price不和expensive搭配,可以说high,low,good.可以改为the other model(或That model,请注意原文中意思有强调了“那个”,用the不够准确)'s price is higher.
2,你的写法OK.
3,i haven't是表示否定的现在完成时,例如I haven't met her before.我从没见过她.I don't have是指你没有某样东西,如I don't have a watch.我没有手表.