Regardless of how you cut it, the job as spec'ed by the client pays a thousand bucks.
Yes, if it was a 'job'.
However, if the client had just asked you to produce & then provide them with a set number of images for them to use, then the question is: For $1000, how many images do they get and what is the agreed Media use, Period of use & Territory of use here ?
Because if for example, a $1000 is for 10 images for 1 years use only in 2 media in 1 region, then should the client want more images or to use your images for longer than that or in more media or in other regions, then naturally they would need to pay more - right !!
So if the client's current budget is only $1000 here, then the unanswered question here is: What would they get for that amount ?
Because the answer isn't '3 days of your time'
unless you are agreeing to do 'Work Made For Hire' or something like that.
For example, a few months ago I had a client tell me before the shoot, that his budget was only £2000.
So for that amount, I agreed to produce & then provide him with 5 images for him to use for 2 years web use only - which he agreed to.
I spent 2 days working with a team of people and produced 7 images in total.
In other words, it cost me more than $2000 to produce those images.
However, after seeing the final results, the client then said he wanted to use all 7 images for 5 years use in Multiple media.
Big difference... and as a result, the amount that he agreed to paid - afterwards - was very different too.
So knowing what it costs you or knowing how much you would like to make, is all very well - but knowing what your images are worth to others, is a totally different thing altogether.