The figures given in the example cited by the original poster are an almost perfect illustration of the common and irrational phenomenon where builders\developers seem able to take almost all the benefit of the S23 incentive, and where buyers seem happier to give money to a builder up front rather than to give maybe the same or less to the taxman in instalments.
If the apartment is selling at €225k, it is reasonable to assume a S23 allowance of 80% of this, or €180k
The S23 allowance has a value equivalent to the tax saving. If you could use it immediately (i.e. if you have a huge rental income), then at assumed tax rate 40%, it has a value of 40% of 180k or €72k. Of course, even with a big rental income, you would pay for it up front, and mightn't get to use it until paying tax (up to 12 months later), so the max real value might be more like 40% of €175,000 - say €70,000.
In the present example, the difference in price between the two apartments (i.e. the cost of S.23 relief assuming the apartments were otherwise of equal value) is €70,000.
QED