I think it will be cheaper for you buy this bag here, rather than in your home country, because the Japanese yen is weak right now and it will also be duty free.
ご質問ありがとうございます。
"I think it will be cheaper for you buy this bag here,"＝「このバックをここで買う方があなたにとって安いと思います」
"rather than in your home country,"＝「あなたの国で（買うので）はなく」
"because the Japanese yen is weak right now"＝「今は円安で」
"and it will also be duty free."=「免税にもなるから。」
ご参考までに。
Since it'll also be tax free, it's more beneficial to buy it here.
ご質問ありがとうございます。
「[免税](https://eikaiwa.dmm.com/uknow/questions/48892/)もできるので、こちらで買う方がお得ですよ」は英語で「Since it'll also be tax free, it's more beneficial to buy it here.」という風に言えます。
また、日本は円安のことも追加したいなら、そうすると、Since the Japanese is weak and it'll also be tax free, it's more beneficial to buy it here.」になります。
ご参考になれば幸いです。
アメリカ合衆国 
