[yariang]

The 25% he alludes to is your recurring mortgage payment, which also happens annually--monthly, actually. What he means here is that a discount of 5% in your mortgage negotiations is much less than an increase of 5% in your salary. So he is right, for the right reason.

[jarek]

corin_ is right - salary is recurring, mortgage/real estate purchase is one-time. You pay off the mortgage with recurring payments, but they are based on the one-time amount. If you negotiate $10k extra salary, after two years you will have $20k extra. If you negotiate $10k lower real estate purchase, after two years you will not have $20k extra. (Technically you will have a little bit more than $10k extra due to compound interest on smaller principal, but nowhere near $20k.)