$1k for an image slider strikes me as completely reasonable. As csomar relates, lots of work goes into something as "simple" as an image slider. That's why (as I mention in a separate comment) non-tech folks will always struggle with the cost of development. If it were easy/fast/cheap, they would do it themselves.

The slider is certainly not a typical one or the one you can find in free/open source. That's not what makes it expensive, though. I bill hourly. There is a lot of overhead

- Writing the right HTML structure.

- Doing CSS work

- Solving some math. equations (fun time)

- JavaScript coding (around 600 lines of code)

- Cross-Browser issues (IE8+) (not so fun)

- Integrating with the client back-end

- Communication (charge for that too)

I can't show you the project as it's private and I'll need his permission, but you get the picture. I'm very comfortable with HTML/CSS/JavaScript. I have a lot of skills and use the best tools available there, and yet, I can't find a way faster.