Aside from any underlying racism, anyone who says that a quarter of a million pounds is "chicken feed" is a pretty big cunt in my book.
There are a few reasons why Johnson (I refuse to simply call him "Boris" for the reason mentioned below) will thankfully never be Prime Minister.
1. It is not exactly a secret in the corridors of Westminster that Boris Johnson is loathed by many in the Conservative party with a number of Tory MPs vowing that if Johnson ever became party leader, let alone PM, they would resign their party membership. When you think that the Tories will nearly always settle differences for the sake of party unity and power, Johnson must be really polarising for the threat of such an exodus to be there.
2. Contrary to popular belief, opinion polls tend to show that the public think he is quite the shitarse. This report from YouGov at the end of last year ranked potential candidates to succeed Theresa May as Tory party leader, and shows that while Johnson had the best response from those who think he'd make a good PM, he also had the highest response of those thinking he'd make a bad PM giving him an overall personal rating of - 37! The only other contenders to achieve anywhere near such wrath are (not surprisingly) Gove and Hunt though far fewer think either of them would make a good PM compared to Johnson. If he was to lead the Tories into a general election, Johnson would probably do a good job rallying a large proportion of troops in the party but he'd be toxic in trying to get floating voters to cast their ballots for Conservative candidates.
3. Outside of the UK, other than those who worship at the feet of Steve Bannon, Johnson is largely regarded as a joke. From foreign comedy & satire shows I've seen in the last couple of years, Johnson is the second biggest foreign punching bag after Donald Trump. If a lot of countries think that the UK is already a nuthouse, what would they think with Boris Johnson in charge?
4. The main reason Johnson is largely still in the public eye is thanks to his journalist background, where he has a lot of networking among fellow journalists and editors of the newspapers that are right of centre, not to mention Darth Vader Rupert Murdoch himself. Johnson along with Gove is probably the biggest conduit for Murdoch to try and influence the government. They have helped him build up the "Boris" brand by usually calling him in headlines and articles simply by his slightly eccentric first name that most people have unwittingly taken up when speaking about him, even those who hate his guts. This astroturfing by his friends in the national press (same applies to Gove in a slightly lesser extent) means that he keeps a higher public profile than one he deserves.