Over 360,000 pedestrians traverse Times Square each day on foot, and that’s not counting the people in vehicles. According to the Times Square Alliance, 40 to 50 million tourists pay Times Square a visit each year. To tap into this massive audience with a billboard ad, you’ll need to shell out about $1 to $4 million per year.
But is it worth it? One way to measure the value of advertising is in cost-per-view, or cost-per-impression. For online marketing platforms like Google Adsense or Facebook, the cost-per-view is typically measured in pennies. Times Square reaches a much larger audience than these online strategies typically can, but the cost is also several times higher per single impression.
However, the Times Square cost-per-view is still lower than that of a Super Bowl ad. Perhaps more surprisingly, the cost-per-view of Times Square ads is competitive with traditional ad forms like direct mailings or newspaper and magazine ads. Time Square costs more than billboards elsewhere in the country, but if you’re hoping to reach viewers outside of the online sphere, it’s actually a pretty cost-effective way to do it.
Quora says around $7K/day although it's unclear if you can rent them for a single day. I would guess you'd need to purchase at least a month.
As for if it's a good strategy, it depends on your user base. Is it a consumer product that spends time in Times Square? If you're a b2b startup targeting tech companies you might have better luck with a billboard in the flatiron district. Also in that Quora thread it says you get about 1.7 cents per impression from a Times Square Billboard.
Alternatively, you could consider picking a core geographic location for your startup and run display ads on every platform you can in order to make yourself seem ubiquitous.