May I ask how many hours you put into it and what the requirements were? I've done quite a bit of custom development but have never had to bill $1k for something as (seemingly) simple as an image slider. Perhaps I'm not charging enough!
While I bill/quote hourly, I usually do my estimate with how many days this will take me. It took me around 2 days to finish this slider. The requirements are not long, and some sliders will take weeks to finish (if not months).