Are you certain? Because all the reasons you've given for the mind-boggling prices for Free Company housing would apply just as much, if not more so, to private housing, especially if they are more affordable.
You will need a greater number of servers and instances and wards to contain the vast array of plots and houses necessary to accommodate all the individual players that want their individual houses. Given that this was the same reason that FC Housing is so expensive, what measures are you planning for personal housing that will stop this from happening?
What will happen if half of those 10 richest players in Legacy servers save their gil to buy up all the personal housing plots, instead of buying the FC Housing as you expect? When you're performing your gil survey, are you going to place buying multiple houses out of reach of these players so that the 99% of the rest of your players have to treat your game like a second job for months on end just to be able to afford one house of the smallest variety? Why not just limit any one FC or person from having more than one plot of land, like you limit any number of other things (I know I can only get one Company Chocobo. Do rich players have the option of getting 2? Not that I know of.)
Are the prices going to be "more affordable" in the sense that, instead of an entire Free Company grinding gil for months and months, it will instead be a single person grinding gil for months and months? I guarantee you that will not make anyone that is complaining now happy either, because the impact is still the same to the individual player, and therefore the end total of gil wouldn't be any more "affordable" just because the total gil on the price tag is less. It will still cost the same amount of work hours per individual player.
So... how can something that will be more stressful on your server architecture be easier to achieve?