Realistically, I'd be surprised if that difference was more than a rounding error for any organization with 500 active developers. $21/month/user is essentially nothing.
In most the big orgs I have been with, price was not the deciding factor, but rather a host of other considerations. That being said if two product where identical in feature's and ease of use, you can guarantee that a significant cheaper product will get further consideration, price is a factor it's just not usually the top factor in big orgs. In a previous life I was an executive at some fairly large companies and personally had 20-30 mil budgets and I can say that at least in the orgs I was with, something 100k+ would get some scrutiny along with some questions as to whether there was a equivalent cheaper product. In many org's purchases over a certain threshold have to be vetted. I know the ones I was with where well south of 100k.
It's $250/person/year. Yes, it's probably a rounding error when you're talking about folks who, with salary and benefits, are almost certainly costing the company $100k+/person/year.