The problem with this reasoning is that while new buildings / tenants may be marginally beneficial to the city, if the rate new condos pay is significantly lower than existing buildings, then fairness issues arise. To me, this is analogous to incentives for building factories, etc - why does the big / new factory get a tax incentive while the small / old one doesn't, if it generates the same spinoff investment / employment / revenue? Put another way, the marginal revenue gain may be positive, but lower than the community average revenue gain (or gain in comparable properties) - how is that fair?