Charters are not always the best way to go when trying to move a large group. I had looked into doing a roundtrip from LGA to DCA on CO on a 737-300 and it was $34,291 or $30,294 out of EWR.

Hyperthetically if you were able to find tickets for $200 each roundtrip - that would equal to $22,800. Thus not a savings to charter an aircraft. I am sure there is a group discount if you do this several times a year.