But there is absolutely no doubt that a college education on average is an economic benefit. The lifetime earning of people with a bachelor's degree are 1.66x that of someone with high school diploma -- again on average. Someone who starts out as a tradesman and ends up with a successful contracting business can do very well for himself, obviously.
Actually, it's not college. Or university. It's any post-secondary education automatically gives you can economic benefit over a high school diploma.
Your skilled tradesman has post-secondary education - in their trade. Be it electrician, plumber, welder, carpenter, etc. There's post-secondary education attached to it. Even the journeyman status is still education - many other professions have a residency or practicum part of the training.
Because the jobs for high school diplomas is very limited - and the supply is wide, so they pay very little. Think janitor or housekeeper, and even then, you're doing minimum wage. There's also retail. All these jobs are unskilled.
Oh yeah, it's possible to make a lot of money as an unskilled labourer - but that's because the job has an element that makes it less appealing - usually a danger element. Crab fishing, say, an industry with a practically 100% injury rate, nasty weather, 60+ hour workdays, etc. But you can easily earn $50K in 3 months. Then there's oilman, working on oil rigs in terrible conditions, but you can get high 5 digits or 6 digits.
But there are plenty of post-secondary education opportunities - college, university, trade school, etc.