You can't stop private business paying the going rate plus a bit more to get the right people in. The pay a politician gets is poor and if you pay peanuts, you get monkeys.
Well as I said I don't think the pay is the main reason there are so many monkey MPs. Plenty of talented people out there earning less than 65k working for schools, health service, small businesses, charities.
And while you can't stop businesses paying what they want, the top salaries in the private sector have grown something like five times more than the average private sector salary over the past 30 years or so - partly because top bosses set their own and each others' pay. Industries themselves should find better ways to regulate that.