That's not what the original aim of the iPad was at all. Take a look at these screenshots from the announcement of the first iPad (thanks 2010 for the 360p resolution):
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The iPad wasn't meant as a miniaturised laptop. In fact Steve Jobs explicitly made a point of this by roasting netbooks, saying that they were just cheap laptops that run clunky PC software. If he were still alive, the idea of putting Mac OS, which has no considerations whatsoever around optimising it for tablet use, like so many people on MacRumors seem to want, he'd have a fit.
He didn't want the iPad to be a secondary device, he wanted it to be people's first choice for many tasks, namely the above ones, and in my opinion the iPad is still unambiguously better at these things than a phone (except music) and a laptop.
In a nutshell, he basically wanted it to be the perfect consumption device. And for millions of people it is. The aim of replacing a laptop only really came in the mid 10s when the iPad Pro came out, and that's still a work in progress. And as for affordability, as some have already pointed out, the base iPad, the spiritual successor to the original, is less than half the price of the original when it first came out, adjusted for inflation.