Considering that you are planning the trip with limited budget and only for 4 days (=96h) you must value both time and money when doing it.
If you use the bus you spend $75 + $75=$150 and 12h + 12h = 24h. This means you spend $150 to enjoy 96h - 24h = 72h of actually camping. This means you pay $150/72h = $2,08 per hour of actual camping.
On the other hand if you choose the plane you spend $150 + $ 150 = $300 and 1,5h + 1,5h = 3h. This means you spend $300 to enjoy 96h - 3h = 93h. This means you pay $300/93h = $3,22 per hour of actual camping.
Considering all that, taking the bus his the most cost-effective option (and the cheaper one also).
