And its getting bigger and bigger by the day, so it should scale. Not increase cost..
I'm pretty sure they do it:
A) for the stock
B) because they are a monopol (almost)
Note: Not defending the increase. Only pointing out there's a possible upside for their market. Yes, at a slightly higher price.
All customers pay for this feature.
When given the choice between credit card or PayPal, customers can get PayPal protection or not for the same price. If they use PayPal they perpetuate the story that people prefer PayPal and contribute to generally higher prices to account for PayPal refunds, mostly damaging themselves in the long run (given we already have laws in place that force merchants to refund / return items and most merchants are not scammers) and benefitting PayPal.
There's a narrative where companies are painted as regretfully rather than opportunistically raising prices, maybe they just want to make more money. That's kinda the point of the system after all
And also the fact that they are one of the few established and widely accepted payment / transfer systems, so their customers aren't going to flee in droves.