It would not take very extensive research to discover that "stipends"  (notionally) are based on the notion that celebrating Mass requires certain physical items, which cost money ...  Hence the idea that for this particular Mass to be celebrated for your intention, please contribute to the actual cost that the celebration entails (cost of the bread, wine ...). In certain places this also relates to whether the priest "should " receive some remuneration, because that is not calculated in what he receives otherwise (differs according to countries, invldun

The analogy is crude, but when you buy a pint of Guinness pulled in a pub it is more expensive that buying a can at your local supermarket. Simply because pulling the pint involves equipment, use of which has a monetary valuable.

The underlying problem here is that the article's author is trying to theologize something that has nothing to do with theology ... (as in when your pastor says "the heating bill for the church is $nnnn.nn")