My band has recently been offered a gig during the opening day ceremonies of a AAA baseball team. The set is about 90 minutes. As a band we've been playing together for about a year and a half and have been playing gigs ever few months. The event coordinator for the baseball team asked me to throw out our asking price for playing the offered gig, and I don't really have enough experience to throw out a good amount.

Does anybody have any experience in this area/can give me a good idea of what kind of price I should ask?

Thanks for the help.
And if you gaze for long into an abyss, the abyss gazes also into you...

The Band

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My bands charge $100-$200 per hour.

For 90 minutes, I'd ask for $150. However, if you need to hire a PA as well, up the price to $200. See how it goes.
And no, Guitar Hero will not help. Even on expert. Really.