India, March 21 -- They're a bit like the novelty T-shirts one buys on impulse; the kind that say "Here for #RishGotHerMan" or "Family Trip Survivor".

Meme coins - a type of cryptocurrency - are easy to make, easy to buy. They cost between a fraction of a paise and Rs.15 per unit. They are churned out, sometimes as an in-joke and sometimes by celebrities, to build on a sense of fandom or community.

And yet. Presidents are now launching them; billions are being made.

In January, US President Donald Trump launched $Trump, so fans could show their support, "celebrate our win and have fun". People have collectively paid more than $350 million for these tokens, since mid-January.

US First Lady Melania Trump launched a meme coin, Melania, a...