The reason it is confusing is simple: This HDFC has broken the law, in a manner of speaking. By law, all HDFCs are mandated to serve a low-income (now median-income) population, and the way that used to be enforced was by putting buyer income caps on the buildings.
It wasn't hard for building residents who inherited apartments and wanted to resell at market to get around that: Find recent college grads or trust fund kids with no income to buy the units. Or sell to foreign buyers who could claim no income or very little income.
It's broken the whole ethics behind HDFCs, which are very heavily subsidized by huge, 40-plus year tax breaks, and made them cash cows for some people.
The way around it? Don't buy in those HDFCs that refuse to follow the rules. They'll find their market of buyers is starved, and stop overpricing these units, which were designed to be perpetually affordable. Buy a unit in a building with resale limits, which will have affordable prices (in the tens of thousands) and a limited increase in property value that goes up slightly year by year. You won't get to retire on the savings, but you can pay for your kids college, start a business, buy a timeshare, or take vacations twice a year as a result of your savings. HDFCs are for working New Yorkers - too sad that so many are willing to sell out for one person's wallet to get thicker. Visit http.uhab.org for more on HDFCs.