Usually not with Google... If you went to Google and said "I will pay you $1M to make a custom version of Google maps for my company with a pink background but no other changes", they wouldn't do it.
Most teams keep the sales guys a long way from engineering, and one customers request rarely makes it in.
$1m is what - one person-year, two? Sure that's not enough. However it doesn't mean the api is custom. Just not the same as the public one. For your specific example, Tesla renders thier own map tiles.
Most teams keep the sales guys a long way from engineering, and one customers request rarely makes it in.