A one night stay in this hotel was originally already cheap at 5000円 but for a limited time it's even cheaper at 3000円
ご質問ありがとうございます。
「元々〜だったのにさらに〜」はそのまま英語で「it was originally...but even」と言います。
また、「このホテルの宿泊料金は5000円と元々安いのに、期間限定で3000円とさらに安くなってるんだよ〜！」と伝えたいなら、そうすると、「A one night stay in this hotel was originally already cheap at 5000円 but for a limited time it's even cheaper at 3000円」になります。
ご参考になれば幸いです。
"The rate per night at this hotel was already cheap at 5000 yen but now its even cheaper at 3000 yen for a limited time offer."
*"The rate per night at this hotel was already cheap at 5000 yen but now its even cheaper at 3000 yen for a limited time offer."*
"the rate per night" 「宿泊料金」
"at this hotel" 「このホテル」
"was already cheap" 「元々安いのに」
"at 5000 yen" 「5000円と」
"but now its even cheaper”「さらに安くなってるんだ」
"at 3000 yen" 「3000円と」
"for a limited time offer" 「期間限定で」
... was originally XX yen which is cheap, but now they're offering ... for XX yen for a limited time which is even cheaper.
この場合、次のような言い方ができますよ。
ーThis hotel was originally 5,000 yen a night which is cheap, but now they're offering rooms for 3,000 yen for a limited time which is even cheaper.
「このホテルは元々一泊5,000円で安いけど、今期間限定で一部屋3,000円とさらにお安くなっている」
... was originally XX yen which is cheap, but now they're offering ... for XX yen for a limited time which is even cheaper. で「…は元々XX円と安いが、今期間限定で…がXX円とさらに安い」と言えます。
ご参考まで！
アメリカ合衆国 
オーストラリア 
カナダ 
