Opportunistic touts are taking advantage of GAA fans by reselling All-Ireland semi-final tickets for more than three times their price.
Many marketplace websites have clamped down on adverts selling tickets above their face value.
However, the Herald has seen Dublin-Mayo tickets being resold for as much as €150 each.
On Adverts.ie, tickets were being advertised at their market value from €32 to €50.
However, in a number of cases, the sellers are reported to have increased the price to exorbitant rates in private messages to interested customers.
Fine Gael TD Noel Rock told the Herald that this week's ticket "chaos" played into the hands of touts.
"Many people who were left without a ticket after lining up for more than two hours were obviously very frustrated and hard done by," he said.
"This plays perfectly into the hands of ticket touts who intend on taking advantage of their desperation to see their team play in Croke Park.
"I've received reports from people who have seen tickets going on sale on the likes of Gumtree and Adverts.ie for way above their market value.
"In fairness to the moderators, they're doing their best to withdraw them as quickly as they can.
"However, many who are flogging them at face value are sending direct messages to people telling them that the tickets are really on sale for way more than the advertised price."
Last year, the Government agreed on new laws aimed at tackling ticket touting, which were endorsed by the Cabinet last month. Anybody trying to sell tickets at above face value can be brought to court under the new laws.
The legislation will also prohibit the use of bot software to buy tickets in excess of the number permitted by event organisers.
It is hoped the legal changes will be enforceable in advance of European football championships in 2020, which will see a number of matches take place here.