There are a lot of things you are leaving out and not considering... you are just taking a linear approach with the CPI, which doesn't tell the whole story. Not all consumer goods follow the CPI consistently. Just to give you a small example, 15 years ago a stick of 128MB of RAM cost around $200.00, and today, for $200.00 you can get 12GB of RAM.
Mario Brothers 3 indeed sold 18 million copies, but it surely did not sell those 18 million copies in one year, or 2, not even 3. It took almost a decade for Mario Brothers 3 to sell that many copies in a market in which Nintendo, early on, had almost no competition. It is highly unlikely that a game would sell that many copies today, or that it would sell consistently in such a long time span, given the current level of competition for gamer dollars and technological advances.
The costs of making a video game may be higher these days... you really can't base such a statement on the number of names you see rolling on the screen, though. Then again, with so many people's names rolling down on the credits, you'd hope that a few of those do quality control. There are many places a company can cut costs, such as no free sodas or movie Fridays, or nor paying $200,000 to some actor to voice 5 minutes of character dialog, rather than cut costs on one of the most crucial parts in the production line. Then again, as I said before, the gaming industry customer is rare in that not only he/she accepts sub-par goods, but thanks the producer of such sub-par goods.
They COULD not pay a celebrity voice actor to voice 5 minutes of character dialog, but that is one of the reasons games cost more these days... every single time Nintendo makes the decision to not include voice acting in their games, reviewers and other people think that's unacceptable ("it's the year 20__ Nintendo, get with the times!","What is this the dark ages?",etc...), and then voice actors weren't good enough, you have to have celebrities (I don't think Danny Trejo only cost a sandwich and a coke to get him in the game, or Wayne Newton for that matter). These are now things gamers expect, along with graphics that are more realistic than what's outside their window. I don't think that's a "maybe" or a point of debate, there's no way the cost of making video games compares to the 1980's, when games like Missile Command were made by one or two people doing all the work, and Fallout New Vegas was made by teams upon teams of people. I mean, if they figured out a way to spend a million dollars in the general development (we're not talking marketing) of Super Mario Bros 3, well... that'd be amazing to me.
With RAM though, you're right that some technology/electronics items have gone down, but that's because cost of producing those parts has gone down because of mass production and more efficiencies/corners cut in creating it (you can bet not as many people were buying RAM in 1988 as they were in 2008 for example, even in the early 90's no one really had a computer in their house, now everyone has at LEAST one, I have three working machines in my apartment). The difference is that's a manufactured item that's probably put together by machines (I have no idea how RAM is produced and could care less), a video game's development is becoming the same as a movie now, and movies have DEFINITELY been effected by inflation ($4-5 to go see a movie in the 80's vs $11 - $15 to see one now). I'm not saying video games now cost more to develop now just because there's more names in the credits now, though the reason there's more names in the credits is because video games cost more to develop now. I would bet QA is one of the first things to get chopped out of the budget in any industry, we just don't know about it. It takes a long time, you need to have the right people doing it (in this case, preferably people with a development background and not just some yokel that likes playing video games for 10 hours a day), and these days you have too many shareholders that are counting on you delivering what you said you would when you said you would, delays mean a dip in stock which means less money for the top dogs, and they'd be PISSED if they found out they're going to have to wait two months to buy their new Benz because someone was working on a bug that is triggered because someone wanted to do a quest out of order.