Haha yep Liz don't worry I did the same when I started pastels, charged next to nothing for them! Always work out how much it's going to cost you in materials, how much time you are going to spend on it and the quality of your drawing skills. Then add the shipping costs onto that. (Always mention when advertising/quoting that extra shipping cost, don't just tack it onto the total cost as they will panic and think it's going to be super expensive!!)
I am absolutely in love with your grey!!! Although it's not all that realistic as you stated, I can really see that you've been playing with those colours underneath to get some depth into it. Once you get some more experience with layering your colours, you'll be able to make them less obvious, so that someone looking at the drawing who doesn't know about how many colours go into it, wouldn't have a clue that there is a heap of green/blue/red or whatever in there, but to look closely, the majority of the drawing actually is those bright, solid colours. You judt don't know it! -hard to explain, that didn't make much sense but after doing a few pastels you'll figure it out haha!