Mosherose –
There are many halachos regarding this issue. All poskim agree that if the goy’s store is cheaper (machlokes HOW much cheaper ), has better quality/more convenient one is allowed to shop at the goyish store. mutar 100%. Many times it is this way because jewish stores are more “mom n’ pop” types and you can get better prices at these company owned stores. (major example – clothing)Goyish stores a lot of times have excelent return policies that are not offered at Yiddishe stores.