Cheap clothes can cost as little as ￥1,000 but for expensive clothes, the sky's the limit.
Cheap clothes start from about \1,000 but there's no limit to how expensive clothes can be.
「青天井である」＝ the sky's the limit / sky-high / no limit
「服の価格は安いものは1000円未満から、高いものになれば青天井です」＝ Cheap clothes can cost as little as ￥1,000 but for expensive clothes, the sky's the limit. / Cheap clothes start from about \1,000 but there's no limit to how expensive clothes can be.
例文：
cheap clothes ＝ 安い洋服
cost ＝ かかる
as little as ＝ ～ほど安い
expensive clothes ＝ 高い洋服
start from ＝ ～始まる
イギリス 
