You want to charge that kind of price for what is essentially peasant food, you should do it in the touristy or CBD area. Not in the Changi Village shithole.
By the way, Malaysians have a weird obsession with petai. I have seen petai sellers in Malaysia, who were holding on to bundles of petai, going to eateries and soliciting diners there to buy some petai. Similar situation as for certain kind of tissue paper merchants in Sinkieland.