Tosfos on Bava Metzia 3A continuing to 3B as discused by Rav Chaim Smulowitz references a "rule" that on Rabbinic swearing we don't say the rule that if you can't swear you pay.

Based on this rule, there seems to be an equivalence of "weight" between a Torah oath and penalty money. The context is Rabbi Chiya's chiddush, and analyzing his kal v'chomer with respect to one's own admission and the testimony of witnesses.

Discussion on the gemara leads me to understand the "mamon" which one's own admission doesn't obligate oneself to is the double-payment penalty money, and not hte principal amount.

And thus that penalty money "mamon" is of comparable weight to a Torah oath.

Now I come to Artscroll footnote 24 on 3b3.

The Torah oath found in Devarim 19:15 refers to the obligation for an oath triggered by a solitary witness... insufficient to impose any bodily or MONETARY punishment.

If my understanding of "weight" in the "either-or Oath or Pay" above is accurate, then I have a contradiction.

The oath of a solitary witness is a Torah oath and in this footnote is claimed to be insufficient to impose monetary punishment, however my understanding of the above "rule" is that the Torah oath is in lieu of payment, or of comparable weight.

Where have I gone wrong?

Chaim Chesler