First of all $150 for a :60 spot is way too cheap. How long did that take you? You are basically working for about $6.00 per hour. Why not get a job at your local Burger King?
You need to figure out what your hourly editing rate is and STICK TO IT!!! You need to figure out what your Daily shooting rate is and STICK TO IT!! Some folks have a 1/2 day rate, but I always contend that I can’t go and find another 1/2 day shoot, so I only charge a day rate.
Once you quote a price, that’s your price. You can’t go back to your client and tell them no, it’s no longer $500 it’s $2,000. You’ve lost all credibility. Consider this a lesson learned. You’ve most likely lost this client. Imagine shopping for a used car, you get a good price of $10,000. The next day the car seller tells you it’s now $18,000. Would you want the car?
By the way, how did you arrive at $2,000 price? Based on what? You need to figure out your rates and guess what?…STICK TO THEM!! In my opinion $2,000 was too low as well.