Saw that Spirit had IAH-DTW RT on sale for roughly $42 if you were a $9 club member (and about $85 if you weren't a $9 member).
I volunteer at IAH, so was already at the airport and went and asked about the price and they quoted me $37.71 RT per person! Nailed it.
Went ahead and appeased them by buying the big front seat. Was $35 extra each way. Happy to do that if they sell tickets to me for under $40!
The IAH-DTW segment had a base fare of $0.01.