Hi, for good prices, can try sites like groupon, or deals.com. usually around $30+Usual price offered by dive centers (without group deals) is around $60 to $90 or even higher.
I just tried my first time ever scuba diving program in Singapore by this website (www.groupon.sg). Bought the voucher few weeks ago and went for this discover scuba diving program organized yesterday afternoon (Saturday, 28 July 2012). Basically it is a 2 hours course priced at S$32 for 1 person at two locations, Outram Secondary School or SAFRA Telok Blangah. Although I was panic at first but this was fun and I will try it again soon.