Well, it is VERY expensive to rent a private jet so it's really not a good option unless you're willing to pay well over the equivalent cost to just buy even first class tickets and will be way way over the price to fly standard commercial fare.

For eight people you might be able to charter a jet in the 'Mid' category such as a Citation Excel or Hawker 800XP, but many jets in this class are not configured for eight so it makes it tougher. You'll also have the jet completely filled to capacity so you might have issues either getting all your luggage to fit or someone might even be sitting on a potty seat. Granted, these have a cover over them that makes it more like a regular seat but it is ... a potty seat.

If you want to be relatively comfortable, you might need to go with a jet in the 'Super-Mid' class, such as a Citation X or Challenger 300. These aircraft are about 25% more than chartering in the 'Mid' class.

As far as rate, the key factors are:
1.) the hourly rate for the aircraft, which varies by model. For Mid's, expect $2700-$3500 per hour. For Super-Mid, $3500 - $4,000.
2.) fuel surcharges. These things burn a lot of fuel, the surcharge will be around another $500-$1,000 per hour depending on the aircraft and operator.
3.) add another 7.5% for federal excise tax, and there's also some other miscellaneous charges for landing fees, and other such fees which are well below the FET tax
4.) positioning charges or 'empty leg' time. When you charter a private jet, you pay for all time that it is flying for your trip - if the jet is based in Farmingdale, NY not Buffalo, you pay all of the above just to get it into Buffalo. If your trip is only a one-way flight, you still pay for it to go and come back as if it were a round-trip...

If this flight is 2-3 hours in length, I would guess you're probably looking at $20-$30K... but you'd need to get a hard quote from a provider to know for sure.

Get more info about private jet prices and types:
http://www.privatejets.com/typical-charter-costs.html