[Client]
We've noticed we gave you the wrong product prices for our new online shop.

[Dev]
Yeah, just login to the backend and fix them.

[Client]
But we don't want to use your fancy backend, we'll be using anyway soon - we want EXCEL!
Could you send us an EXCEL, so we can fix that?
How much will this cost?

[Dev]
Sure... here you are.
Not that much, takes about an hour.

[Client]
Great, you'll hear from us in a few days.

(a few months later...)

[Client]
We've finally managed to update the EXCEL. And btw, we've also added a bunch of columns with product pictures and new properties, highlighted products to delete red, inserted some comments with manual instructions and basically destroyed the entire data structure of this table.

Before I forget... also make sure to get this finished today, we have to go live ASAP. Our marketing campaign is already live.

[Dev]
Well, I'm sorry to say this, but this is not possible.
I'm currently working on another project and it will take me hours to clean up the data you sent me, before even starting to build an import tool for the new data you provided. Better stop the campaign and I'll do my best to get this done by the end of the week. Also it may be a bit costly.

(angry client calls immediately...)

(dev transfers to manager...)

(client transfers to client's boss...)

[Manager]
Ok Dev, I think I was able to explain it to them. However, it would be great if you spend day and night to get this thing out ASAP.

[Dev]
No problem...
I'll just do it by hand to get this out immediately.

(few days later; nearly done, exhausted)

[Client]
Hey Dev, here's another EXCEL.
We've just noticed there were a bunch of errors in the previous one. Please use this instead...