I have a very simple rule, if it isn't something special, then $100 is my absolute limit. By special I mean like a wedding dress (event), Riding boots (Occupation), or a really nice winter coat (protection). So, if I am paying for fashion then $150 is right out, but if I am paying for something else maybe.
In practice the only thing that ever bumps into this limit is shoes. I would probably have a really tough time paying anything more than $50 for some jeans. I buy clothes second hand more often than new and usually speaking, I tend to spend less than $20 on jeans.
Also even if the clothes item is special, I have another rule that is unless I am doing something on a competitive level I will not spend over $1000 on anything not transportation, health care, education, or housing related. So, no $5k wedding dress in my future, nor $2k vacuum cleaner, but a $20k car is something reasonable.