Kind of off topic but the actual "Santa isn't real" moment for me was that some children
really believed it. To us, it was always on the same level as the fairies (led by BDFL Tinkerbell, obviously) in my grandmother's garden or the tooth fairy: fun to imagine but clearly, literally, make-believe and I thought everyone was just playing up to the same fun thought-experiment.
And, indeed, the Argos catalogue was, for me, pored over all year round. In turn I discovered the multi-volume RS print catalogue and real desire set in. Sadly Santa didn't have a trade account so took a while to scam an account that permitted no-lower-limit free shipping.