Separate three offers: a public gallery, a one-off signup allowance and credits that refresh. Only the latter two necessarily describe access to generation, and neither guarantees that every model or export size is available. Sexy.ai's recorded free access is gallery browsing. Promptchan and SweetPorn advertise recurring generation credits; CreamPorn records a signup allowance.
Compare what one finished image costs, not just the number of credits in a pack. Ask how many credits the intended model uses, whether an edit is charged again, and whether upscaling or downloading costs extra. Keep a note of the billing period too: a one-time pack and an auto-renewing subscription are different commitments even when their displayed prices match.