To be fair, Wizards mentioned that in '91 there were SNES games that were $50 and $60. That's true, but most of the $60-70 were expansive RPGs like Squaresoft titles that gave you 60-80 hours of content often times. Most other games couldn't offer that kind of content, a lot of games were designed to be beaten in a day or two, or even an evening. It was almost silly to consider we paid what we did for those games! These days I don't even spend $40 on a short game I can beat in an evening, I just wait till it's $20 or less either in a second hand market or on Steam.
Also, things are a bit different today when it comes to the video game industry. Doing some research on Kotaku, games in the early 90s were expensive relatively speaking. The industry has made advances in manufacturing over the years which helped alleviate the high cost of producing games. Digital copies are one of those ways. Also, back in the day 3rd party companies used to have to pay Nintendo large royalties to release games for their systems, and the consumer ate those royalties. They had to find ways to cut costs to keep the valuation constant as I'm sure most of them realized the average consumer wasn't going to regularly spend $80-100 for a video game. Back then that was nearly the cost of a system!
As far as the second hand market, I'm partially on the fence but I definitely lean towards needing that market. Personally I don't sell my video games anymore, at least not at this stage. I keep everything, mostly because I'll get nostalgic for some games and I end up wanting to play them again. There are some real stinkers I've bought over the years that I probably could offload, and some are worth good money due to their rarity, but I'd rather just collect at this point and hoard them. That said, I've bought used games in the past and will continue to do so. If people want to sell their games they SHOULD be able to. When you purchase a game it's yours, you should be able to do with it what you want. That gets sketchy when we're talking digital copies, but in that case you're purchasing a license and not a physical copy, which is why I always go for a disc when possible. I do think eventually the industry will go almost entirely digital. I don't know if they'll ever go completely digital though. As long as the internet isn't free, there will be a subset of gamers that will want offline content that doesn't require you to download a game.
As far as the whole digital market and legacy games, the argument is kind of invalid when it comes to availability of old titles and the ability to run on today's machines. While it's always going to be easier to buy an older game like Sim City 2000 as a digital Steam rerelease, times have changed and it's not that difficult to get many games to run on today's systems. A lot of those old DOS based games can be run in utilities like DOSBox with little setup to get them to run. I'll admit I've rebought a few of my old games, like Fallout 2, because it's easier just to launch it in Steam rather than tweaking it to run on Windows 7, but I've made adjustments to my older games like KOTOR, Imperialism, and TIE Fighter to get them to run in my current Windows box.