So I have to recoup that cost. I pass that cost onto all of my customers by mixing it into the cost of goods and services. If you buy things from me, even if you are not a subscriber to google/yahoo, you have in effect paid for those services. This is somewhat invisible to the people with those email addresses but does actually affect them, if only a little bit.
Google would tell you that you can simply start with a low volume and ramp up slowly. In reality this is simply not practical for most businesses. This gets into discussions around queue-per-domain management and rate-limit-per-domain, but quickly falls apart when you have to notify a large number of your customers on a time sensitive transaction that is out-of-band from their web browsing experience. A modern work around is to have a cell phone application for notifications rather than email assuming you let your own customers choose that over smtp in their profile. Another work around is to use an email campaign provider that already pays into the whitelists, but then I have to give your email address to a potentially shady company that may cross-sell / cross-market to you.