The use of so-called dynamic pricing saw tickets rise to over 415 euro for standard standing tickets.
The consumer watchdog has received over 100 complaints about the experience of buying Oasis tickets for Croke Park.
The CCPC says while companies are allowed to respond to demand - there are what are described as 'legitimate concerns' over how people were treated.
It has now opened an investigation to see if consumer protection laws were broken.
The watchdog is also accepting more complaints about the experience of buying tickets.
Oasis are playing two shows at Dublin's Croke Park next August, and announced a comeback - 15 years on from breaking up.
IN a statement the CCPC said:
"The CCPC has reviewed more than 100 contacts from consumers who are very disappointed and frustrated about their experience of buying tickets for Oasis concerts," said Brian McHugh, Chair of the CCPC.
"While companies in Ireland are allowed to respond to market demand, there are legitimate concerns over how consumers were treated and we have decided that an in-depth investigation is necessary."
"If we find that consumer protection laws were broken we will take action."
