Right now in Virgo, there are no items for sale, of any kind. I wondered why so I looked, and the answer is, the prices are so low that no one would ever list them.
E.g., right now the maximum price in metal for a bronze metal booster is 92,444. Now, no one would sell a metal booster unless they got more for it than they would reap by using it. So, for a 10% metal boost on one planet for a week to be worth less than 92,444, their hourly metal production would have to be less than 5503. That's a level 9 or 10 metal mine, even with no crawlers and no class bonus and no plasma technology. So, no one will ever sell a metal booster. Conversely, since I produce 725k metal per hour, I'd be willing (in theory) to pay up to 12 million metal for this item, and in theory so would anyone with comparable mine levels. The price should be ten, twenty, a hundred times as high as it is.
Similarly, right now the maximum price for the Kraken, Newtron, and Detroid are all in the tens of thousands metal for bronze, and a quarter million for gold. 15 planet fields maxes at 11m metal, and 6 moon fields at 4m. Class switches are 18m metal, maximum. That last one is a 500k DM item whose maximum price is my metal mine production on one planet, for one day. No one's ever going to sell items at these rates.
I know the marketplace in theory is supposed to adjust the rates in response to people's buying and selling behavior. I've seen it happen with the prices of the Crawler and other things. But right now, the prices of items are so low that the market won't ever get any activity with which to update the default prices.
So, I suggest that you make the range wider and bump the default prices a lot, so that some activity starts appearing, and the market can find the right price.