It might be a good deal. It might not. A more important question will be the portion of the option price that you get paid up front. Let's say the budget for the pilot is $1M. That means you will get paid $40,000 IF the pilot gets made (and depending on his conditions, possibly picked up). An option allows the Producer to pay you a nominal fee up front -- which could be as little as a $1 -- then you get paid the full option price when certain conditions are met: like the series based on the pilot gets ordered. So, the first thing you need to understand is that you will not get the 4% just by signing the option. You will get some small piece of that.
For reference, I looked up the WGA Median for a 1-hour pilot and it's $175K. I'm guessing you are not a WGA writer, so that may not mean anything, but it is a reference point.
Other points you will have to consider in the option are the length of time of the option (maybe 1 to 2 years) and if the Producer has the right to extend it -- usually with another small payment to you.
Bottom line, when that option agreement arrives, you need to have an attorney review it. You need an attorney with lots of experience in motion picture and tv production. That's the person that will let you know if you are getting a good deal.
