I know very little about this topic area. I believe a vetitum is imposed to delay a marriage until a given condition has been fulfilled, for instance, till the removal of the obstacle to a marriage arising from a preceding betrothal to another person. It may be that your friend has a defect in her status from a prior marriage etc. that makes her eligibility for marriage pending satisfaction. It sounds like her Catholic husband found something in her past and wanted to “red flag” it so other Catholics would not fall for her misrepresentations of being eligible for marriage. This is probably why he never married her - and since he went through the process of getting a church ruling he is probably annoyed that she mislead him about her eligibility for marriage in the Catholic Church. He may have requested it be held in the Church record for future Catholic"suitors" to save them other Catholics the time and emotional energy of falling for her false pretenses of eligibility. I think this is fairly rare.
I doubt it is a simple matter of paying to have it removed - it would be a fee to re-open a case of inquiry and see if the conditions that prevented her prior eligibility for marriage have been removed (perhaps the death of a prior Catholic spouse?).
Interesting though that the Church uses these still - but not in the least surprising that some protestant would take it as an opportunity to polemicize it into a cash cow opportunity for the church when its a real spiritual deficiency caused by invalid single vice marital status. I doubt that $850 would even cover the true costs of the administrative actions and investigators time to resolve the case.