Also keep in mind that while you have until Tuesday to decide (see Section 4.15.1), you have until April 10 to actually come up with the money if you can secure a Commitment Letter from a sponsor or purchase order from the school in the meantime. See
here on the FIRST site for the details. There are risks, obviously, in writing a PO for money you don't have--your school will surely enlighten you about them.
Don't forget about travel, either. The best airfare on Travelocity for LAX to ATL for Wednesday-Sunday is $350. Then add hotels, food, MARTA passes, the FIRST Finale tickets if you wish to attend, and you're looking at a significant cost to get any size of team there and back.