I pointed out a difference like that once to the CTO, who then proceeded to show me the financials for the service. We were making something like a hundred thousand dollars a month from it (i had no idea, seemed like we only had a few clients... but they paid A LOT). $400 wasn't worth spending time thinking about. Especially if it might cause downtime.
Company I used to work for happily paid company A four times what company B charged for the exact same service, just because company A was willing to send quarterly invoices in way that played nicely with our invoicing system. For companies, saving a few hundred bucks here and there often isn't worth the hassles of introducing any extra friction.