Star Trek 4 is set in 2286, 20 years after the end of TOS and at that time Kirk says "we don't" use money. I don't think it was intended as something that just happened before he headed out to get Spock's body.Money was still in use as late as TOS in the classic timeline. It's only in the newer series that the 22nd century is identical to the late 23rd.
Why again was it that 22nd C. shuttlecraft have warp now? Is it just because TOS gave them thingerdoos before thingerdoos were canonically established as warp engines? Even though TMP actively retconned it with what is now widely misunderstood as the "Vulcan" shuttle?