Aphex is on the money re OD-ing (chemically speaking), it just can't happen from psilocin alone, and your body passes the excess anyway, while your receptors are all used up/ there's nowhere for the spilocin to actually act once it's flooded the system, it just degrades/ is excreted... u might also be interested in the thred titled "CAN SHROOMS KILL YOU" or sommat' along those lines... some good sourced info there...
Good approach you have at 3g dose, way better to have a 'low level/ mild' trip than a bad one, hey, you can always up the dose the next time you decide to indulge... much safer/ conducive to good experiences that way !! Don't worry too much about price, as long as it's not outrageous... the main consideration is trusting the person you get them from... I'd never buy shrooms, but thaz' easy for me to say I spose, if I HAD to I'd not do it from a stranger, and I'd be thinking the price probably fluctuates according to availability/ competition, like the price of pot... I'd certainly be willing to pay top dollar to someone I 'knew' as opposed to a few bucks to a relative stranger, if I ever was going to buy anything I planned to eat ...