Hello. I'm pretty interested in your project.
However I cannot give you a real quote until I know the details of the changes you want to add to the original pastebin code.
There are lots of open source repositories for pastebin, including the original one, that will accelerate project start. But depending on the features you want to add, it will be the time spent and so the cost.
So, consider my current bid as a full day work (8 hours x USD $30 / hour). Once I analyze what you want to change/add, I'll give you my time estimation and we can arrange the hours then.
I hope you consider my offer seriously.
In any case, please share what you want changed/added to pastebin, so I can analyze it and give you a real time estimation and quote.
Thanks.