It depends a lot on the amount sent. If it is a high-value transaction, I am willing to pay a higher fee, if it is a low amount, it will be better to use an altcoin. Of course, this is for quick confirmation, we do not always need it to be fast so we can wait.
I can do money transfers using my online banking account for free and in an instant for as long as they are within the same bank. But this will soon change as my bank has a new policy where they would start charging even bank to bank online fund transfers. With bitcoin, anything that doesnt cost over a dollar for transactions below $100 for me is fair, just as long as the transaction speed is almost instant or faster than they currently are. Fees should also be bracketed according to amounts to be transferred, but shouldnt be too high so as not to turn off potential users who would otherwise just use the money transfer services elsewhere.
For a bigger transaction maybe i am willing to paid more than 1$, but for 10$ maybe i will satisfied to pay 0.1$, but it depends on the importance of the transaction, if it is an important transaction that need to be confirms immediately i am willing to pay more than 5$
yes it depends on the amount and of course the service. If the transaction service is too good anyone will agree to pay more than average fee on other sites. And I think the highest possible fee should be 3-4% of the amount of transaction. And yes they can charge more with the agreement of user for providing more facilities.