The average Prime user doesn't shop around or comparison shop. If you really do you are an exception and not the typical prime shopper. Prime users feel compelled to "get their money worth" by using the service more and they think of their shipping as free where it is actually prepaid. Getting someone to prepay for shipping for a whole year is a great way to create loyalty.
Honestly, I, personally, don't understand Prime but I also don't buy very much stuff and don't find getting my stuff in two days compelling 99% of the time so I wouldn't spend even close to $100 on shipping. I very, very often buy my basics online (TP, paper towels, pet food, soap, etc.) but I just wait for a sale from any retailer to buy. Other than basics I rarely buy much else.
Honestly, I, personally, don't understand Prime but I also don't buy very much stuff and don't find getting my stuff in two days compelling 99% of the time so I wouldn't spend even close to $100 on shipping. I very, very often buy my basics online (TP, paper towels, pet food, soap, etc.) but I just wait for a sale from any retailer to buy. Other than basics I rarely buy much else.