It isn't that new coins can't be created, a coin may be worth e.g. $100 and it costs $101 in electricity to create another one so nobody does until the demand for coins increases.

But the amount of work required to validate a transaction need not be as much as it takes to create a coin, and people will continue to be willing to pay someone 5c to do 4c worth of computation to validate their transaction.

Yep, a non deflationary currency would be precisely one that has its coins created all the time, instead of in a predefined amount as bitcoins. (You can think of mining as "discovering" one of the predefined bitcoins instead of creating a new one). The problem is that for a currency to be slightly inflationary, as it should be, you need to tie it to an economy and make political decisions about it- and then you're back at square one.