An ability to artificially make humans smarter would, however, likely be one that came at a hefty price and thus could only be afforded by the well off
I can see where you're going with this but disagree. For decades we've had steroids that can make us stronger, and plastic surgery that can make us more attractive. Neither is particularly expensive anymore nor are they the preserve of the rich.
you would end up with a much bigger divide than we have now, where some people, due to family wealth, simply had more potential for intelligence then poorer people
We already have that now. Wealthier people can privately educate their children or buy houses close to better schools to increase the educational potential of their children. The rich can pay for private tutors or private schooling, whichever they feel gives their offspring the best chances.
The best university placements and highest paid jobs would go to those people, perpetuating the cycle.
I was the first generation of my family to attend university. I may have only managed grades to gain entry to a regional seat of learning rather than oxbridge or Durham, but graduating gave me opportunities to move my family up the wealth scale a notch or two.
My children will as a result be able to attend a better school than I did, and hopefully gain entry to a more prestigeous university. Assuming they are in any way academic, otherwise I can help them train for a trade and setup in business after a few years as an employee.
Parents with an interest in their children, regardless of fiscal attainment, will always find ways to improve their potential intelligence within their physical limits. To me, the original poster seemed to find ethical dilemma not in that, but in tweaking (scientifically or artificially) a persons maximum capacity for intelligence. I still see nothing wrong with that, and would expect it to drop quickly in price such that all can afford it. I'd certainly see value in it.
Genetics must surely play a part in IQ, more so than money in my view. Wayne Rooney is not smarter than I, and I'd bet every penny I have that his children won't be smarter than mine.