Given that Mozilla's budget is over $10M per year and Firefox has been under development for over 10 years, saying a browser costs $1B is off by less than one order of magnitude. Considering that the author is complaining about confusion of 5-6 orders of magnitude, I find this simplification excusable.
Mozila didnt start from scratch. It started by open sourcing what netscape was. So you need to add those costs/ years in the calculation. I mean even if they rewrote it completely, these man years should be added in the estimation of cost.
