The problem with price guides, is that pro-price guide people refuse to accept decent, non-raping values that most people either do get the games for or would only pay for them. They seem to only be looking for gouging guides.
Sold prices don't tell the whole story of a game's value. Asking prices that don't sell are only the tip of the iceberg. Any game's true value is what the most people would pay for it and with a market like the TG-16, what most people would pay isn't advertised through potential sales.
If 90% of Turbo shoppers would pay as much as $5 for Keith Courage, but it usually goes unsold at higher asking prices, because it's rarely listed as low as $5, its value is actually <$5. This figure wouldn't be revealed in all the unsold listings, you'd only get a feel for it by talking to members of the community. If there are a few sellers regularly listing KC for $100+, the true value is still $5. If for whatever reason(s), every once in a while someone is foolish enough to buy KC for anywhere between $10 - $100 or more, the game's true value is still $5.
So we could get together and make a date-proof price guide that would reflect what most people would pay for each game, but judging by the comments of most pro-price guide posters who have visited the forum, they would dismiss it as fantasy. I'm guessing that most price guide searchers are more sellers than players or fans. Who are interested in potentially someday flipping the games they buy, even if the play them a bit at first. The arguments against anti-price guide logic seem to be from investment/seller/collecting-for-the-sake-of-collecting/etc perspectives, which all justify sellers guides, not buying guides.
If 90% of the people who actually buy Turbo games would only pay $1 - $100 for Magical Chase, then MC's dollar value is <$100. The rare $2000 sale prices don't average the value out, it doesn't work that way. If you believe that it does, then price guides are useless to you anyway. The rare super low prices sales actually do affect the game's value though. If you are a buyer. If you'd never pay more than $100 for a game that sells at times for $50 and at times for $2000, and almost everyone else would rather not buy it all than pay more than $100, then the $2000 sales are meaningless unless you are a gouger interested in manipulating the market.
Even if you are the kind of person who would average in the crazy high sales into the equation, along with low sales and what most Turbo buyers would actually pay... you're still ignoring what most game fans who are not regular Turbo buyers would pay, along with what the rest of the world would pay. If you're going to factor in what anyone would pay for MC and not just what almost all Turbo fans would pay, then its value to the average person is really about a penny.
Even with the occasional ridiculous selling prices of Magical Chase, all that it has done is made it so that Turbo fans rarely buy it. The reason almost all Turbo fans don't buy it anymore? Because it's not worth what most people are asking for it.