Tickets for next Saturday's Ireland v England Six Nations clash are being offered for sale for almost €7000 at a time.
he Dublin clash, which is likely to be a championship decider, is a sell-out.
But hundreds of tickets have appeared on the black market via ticket resale sites - at vastly inflated prices.
In one case a single ticket was last night being offered for £6,076 - nearly 70 times the official price.
Another was on sale for €3910, and a third for €3900.
The tickets are on Viagogo - a secondary ticket site - where the cheapest seats start at £545.Tickets were officially priced between €30 and €105.
The news has infuriated fans unable to secure tickets for the eagerly anticipated clash.
If Ireland beat Wales tonight, they could win the championship with a victory over Eddie Jones's side at the Aviva Stadium.
England also know a win in Dublin will see them eclipse New Zealand's record of 18 consecutive victories, provided they beat Scotland tomorrow.
A supporter who flagged up the extortionate resale prices said: "I am a massive Ireland fan, yet always struggle to get tickets.
"To see loads of tickets on sale for prices that no ordinary fan could ever afford is a real kick in the teeth."
The Republic's government is considering measures to address ticket prices. A Private Members' Bill by Fine Gael TD Noel Rock and Independent TD Stephen Donnelly would ban the resale of tickets for above face value, with the exception of charity auctions.
A spokesman for the Irish Rugby Football Union (IRFU) warned they could trace people trying to cash in on tickets.
"Unfortunately there are no laws banning the sale of tickets above face value, but the IRFU is encouraged that there are proposals at government level to address this area, as we believe that a crackdown on the practice will only be effective if legislation is developed, and we support all efforts in this regard," he said.
"Our advice to fans is clear: do not purchase tickets from unofficial sources. All tickets issued through official IRFU channels are traceable to the individual purchaser.
"When the IRFU becomes aware of tickets being resold, above face value, we follow up with the original purchaser, where sufficient information is available to identify them, and we request that they desist from the practice, or their ticket will be cancelled."