Yeah I agree. Knowing that the chance is so high, it would likely have drawn a lot more people in. £30 for a potential £250 gun? That's a great gamble by any measure. Especially since there will be more prizes in the future.
Though pointing it out like that would seem like a slightly convoluted form of bribery, if you see what I mean? Since the more people join, the lower the chance actually is, so it's sort of recruiting people under false pretences. Though then again, I imagine everyone that did join up off the back of hearing that, would understand that by joining, they increase the odds.
It's a catch 22.