This is a very manual solution but at the end of each month you could increase your current month’s Targets, to cover your additional spend, since payday & then descrease the following month’s Targets to take that spend from your new paycheck into account. That way your performance against Target is always measured against the same benchmark & the category alerts 
will still work as they should & provide a meaningful insight.
Obviously that’s going to be too much hassle for some users but it’s what I do at the moment 