I will make a trailer for any game, all you have to do is send me gameplay then I will edit it, add music, text and make it look AMAZING! When I finish I will put a watermark over so you can see then say how much you think it is worth. Thank you!
You’ll probably get more replies if you show any previous work.
Also you need to supply more information. What is this music you’re talking about? Do you have rights to use it?
As for your way of working I really think you shouldn’t work first and then let the customer say a price once it’s done. Respect your work man, you set the price and it should be stated in a contract so you don’t get screwed over. But it’s all up to you.