I am advised by Revenue that each 1% reduction in the headline rate of CGT is estimated to be €32 million, assuming no behavioural change. Therefore on a straight-line basis the cost of a cut in the CGT rate from its current rate of 33% to 25% is estimated to be €256 million.
The Deputy may be interested in the analysis included at link: https://www.revenue.ie/en/corporate/documents/research/capital-taxes-profile.pdf, which includes information on the incomes of individuals making CGT payments - see Tables 12 and 13 in particular. As can be seen CGT is paid by individuals across all income deciles and therefore any change to the CGT regime would impact all income deciles.
Finally, the Deputy should note that any changes to the CGT regime are considered in the context of the annual Budget and Finance Bill process.