Depends on the bank. In Germany, N26's free account charges 0.49€ per instant SEPA transfer, and sometimes it's unavailable because the other bank (e.g. one used by many German doctors) only supports non-instant SEPA.
But yes, instant SEPA is often free and often available and very nice when both of those are true.
Last time I checked instant sepa (which was today) it was free as in zero commissions on either side and was actually instant.