When Nassim Taleb's predictions fail and someone points that out, he calls that person fucking idiot.

The main complaint seems to be that Taleb violates an orthodoxy and not that he's factually wrong. On the issues of costs the cited paper says:

This cost-saving potential has been supported by several studies that compared homeopathy with conventional medicine. However, our own health economic evaluations did not show a consistent picture. We observed no differences in costs [15] or additional costs [16,17] in the homeopathic group compared to conventional care depending on the setting or diagnosis. [...] A recent systematic review by Viksveen on the cost-effectiveness of homeopathy showed that in eight out of fourteen studies, the homeopathic treatment was less cost-intensive than the conventional treatment; in four studies, the treatment costs were similar; and in two studies, the homeopathic treatment was more costly than conventional treatment

There are observed cases where homeopathy did lead to cost savings as Taleb suggests.

Interestingly the cited PLoS paper puts people who don't take homeopathy into the homeopathy group based on the fact that they could get it for free:

For this analysis, patients belonged to the homeopathy group if they subscribed to the integrated care contract in 2011 and if they were continuously insured through the TK for the observational period (12 months before and 18 months after subscription to the integrated care contract), regardless of whether they used homeopathy during the study period."