Dealers charging a fee for using a credit card

I’m wondering if this is the new trend of dealers charging customers anywhere between 3 and 4% fee on the total sale if paying by credit card?   I was going to buy a brand new item online for 5K, but stopped dead in my tracks when I found I was going to have to pay a 3.9% fee for using my Mastercard!  The fee would have been almost $200.00!   Since this dealer has mostly online sales, it sounds like a big money grab to me. Between the 5K price, add $275.00 for shipping and 200 for paying by CC plus sales tax of $300.00, it would have cost me $5775.00.  I cancelled before I clicked send.  I called the dealer and was told that is the cost of doing business on the internet, so I basically told them to pound sand. 
 

Two weeks ago, I had all new brakes and rotors replaced on my 2020 Tucson with only 22K miles on it.  The bill was $1375 and I paid with my card.  When I got the statement, there was a CC fee of $37.00 added to the bill.  I went back to the Hyundai dealer and was told all businesses do this and he pointed to the sign.  I told them I saw the sign but paid with my DEBIT CARD, not a CC.  I was told it didn’t matter.  When I asked how many transactions were in cash, the service writer told me one out of fifteen pay in cash.  This makes me sick to my stomach.  
 

I would like to hear from others who have dealt with this.