I can tell you that a load of contractors for a big project wrote 15000 LOC (each) in a year. That's an incredibly rough answer, but it was useful to us as we have 400,000 existing C++ LoC and we could figure out that converting it all to C# would take us about 26 man-years to complete. Give or take. 

So now we know the rough order of magnitude, we can plan better for it - getting 20 devs and estimating a year's work for them all would be about right. Before counting, we didn't have a clue how long it would take to migrate.

So my advice for you is to checkout all the code you've written in a specific amount of time (I was fortunate having a fresh project to work with), then run one of the many code metric tools on it. Divide the number by the time and you can give him an accurate answer - how much LOC *you actually write* per day. For us, that came out at 90 LOC per day! I guess we did have a lot of meetings and documentation on that project, but then I guess we'll have lots of meetings and documentation on the next one too :)