Go to Geico's website
www.geico.com.
Look towards the bottom of the page, under "Geico Portfolio" you will see a link for "Life Insurance" (select it).
After putting in certain variables (including zip code, age, etc.), you will get a series of quotes. You can see what the prices are at different levels of coverage (and even by payment plan: annual, semi, monthly, etc.). Play around with the numbers. You may determine there is a sweet spot (i.e., $500K is only pennies more than $250K). As an aside, be sure to consider the impact of inflation on the policy coverage.
These quotes are actually generated by LifeQuote.com (but going through Geico reduces the chance you need to enter your email address for spam).
I'd use these quotes as the benchmark for discussions with your Agent. Don't be afraid to go outside your agent for better pricing on insurance coverage.
Good luck.