You are Lord Kelvin and I claim my £5
I am quite aware that I couldn't build a mobile phone in my garage from sticky back plastic and straws . In fact the list of things that I take for granted that I have no skills and inadequate knowledge to produce is a lot longer than mobile phones. Given enough iron ore, charcoal, clay and a few years experimentation I might manage a crude paperclip. However luckily man is a) a social animal, b) capable of specialising and c) callable of innovating.
I don't realistically expect to see a space elevator in my lifetime. I doubt my children will see one. But in 3 generations we have gone from horse and cart to the moon, quill pen to streaming downloads, morse code to the internet, so who would bet against astonishing developments in the next 150 years?