Walt didn't let Jane die because he disliked her, he let Jane die because he thought it was the only way to prevent Jesse from overdosing.
What's most gut-wrenching about that entire sequence is that if Q hadn't gone easy on Jane and followed through on his threat to call the cops he would have saved her.
no, he let her die because she was bad for business.
Where on Earth do you get that from? He went over to the house that day explicitly because he knew two junkies with a duffel bag full of money would be dead within a week, and after that incidental conversation with Q he didn't want to just let that happen.
If he cared that much about things being bad for business he would have killed them both and made it look like an overdose.
Remember when he saw her choking on her vomit, he started to move toward her to help. Then he stopped, and when she stopped breathing he started to cry. He decided in that split second to sacrifice Jane to save Jesse.
That certainly doesn't make it okay, but it certainly was not a utilitarian move on his part. Walt at that point was happy to work for Fring and never see Jesse again.