I’m booking my first cruise with Celebrity in 7 years and I agree completely. I watch my pricing constantly. Same promotion, same cabin availability, but prices fluctuate often, often multiple times a day. Package pricing is way over the top. Single rates are more than 2 times the fare for per person couples. Singles are cut out of guarantee rates.
The issue OP shows is especially egregious. It is confusing and, yes, illogical.