Even though our (now closed) business was well known in our field for over 30 years, our eBay customers and many of our other online customers mostly preferred to use PP rather than to give us their numbers directly.
Since we did not keep customer numbers on file, they had to type in the whole number every time which might have been a factor.
And yes it is expensive. There is a reason why convenience stores for example will not take debit or cc payments under a certain amount, usually $5 or so.
The rate you pay the CC company is partly based on how much your average sale is. The smaller the payment, the higher the interest rates.