Was I U with this reply?

[CrohnicallyPregnant]

Selling something locally, arranged collection for today at 4:30pm as buyer needed to come before 5pm.

By 4:55 they hadn't arrived, and sent a message saying they were sorry but unable to make it, and they would let me know when they could.

I replied "don't bother, you have wasted our time!"

I wouldn't have minded so much if they had let us know before the arranged pick up time. So was I being too harsh?

It was quite harsh but equally they have wasted your time so I get why you're annoyed. They should have let you know before 4:30pm, or if there was a good reason they couldn't do so, to explain that. They also should have asked when was convenient for you in terms of coming back, not just saying they'd let you know when they could and expect you to fit in.

I don't give people a second chance to waste my time - just block them and re-list.

Not harsh at all. I can't abide such rudeness. As they'll let you know when they can make it. Oh how kind of them . Muppets.

No they did waste your time, and would probably do it again if you gave them a second chance

Harsh message. I may have worded differently, e.g. "ok, but the item is now back on the market"