Short answer. As a percentage of the auctioned item's value. Article 185 of the Revised Penal Code imposes, alongside prision correccional in its minimum period, a fine ranging from 10 to 50 per centum of the value of the thing auctioned — so the fine scales directly with what the item being auctioned was actually worth.
What the law says
Any person who shall solicit any gift or promise as a consideration for refraining from taking part in any public auction, and any person who shall attempt to cause bidders to stay away from an auction by threats, gifts, promises, or any other artifice, with intent to cause the reduction of the price of the thing auctioned, shall suffer the penalty of prision correccional in its minimum period and a fine ranging from 10 to 50 per centum of the value of the thing auctioned.
Revised Penal Code, Article 185 — Machinations In Public Auctions. Read the full provision →
The fine is a percentage of the item's value
Article 185 provides that the offense carries a fine ranging from 10 to 50 per centum of the value of the thing auctioned, on top of prision correccional in its minimum period. Rather than a fixed peso amount, the fine is calculated as a percentage — somewhere between 10% and 50% — of whatever the auctioned item was actually worth, so a higher-value item being auctioned results in a correspondingly higher potential fine.
What conduct triggers the penalty
The article covers two related acts: any person who shall solicit any gift or promise as a consideration for refraining from taking part in any public auction, and any person who shall attempt to cause bidders to stay away from an auction by threats, gifts, promises, or any other artifice, done with intent to cause the reduction of the price of the thing auctioned. Either act, if done with that intent, carries the same combined penalty of imprisonment and the percentage-based fine.
Why the fine is tied to the auctioned value
Pegging the fine to a percentage of the auctioned item's value, rather than a flat sum, connects the size of the fine to the scale of the manipulation. Rigging the auction of a high-value item stands to depress its price by a correspondingly larger amount, so a fine calculated as a share of that value scales the penalty to the harm the scheme was capable of causing to the seller and to fair competition among bidders.
What the article does not spell out
Article 185 sets the range for the fine — 10 to 50 per centum — but it does not itself specify how the value of the thing auctioned is to be determined or proven in a particular case, such as whether it is the appraised value, the reserve price, or some other measure. That determination depends on the evidence available in the specific case being prosecuted.