Right now, we can only buy or sell 100 energy for (Last time I checked) about 6000 crowns.
Why not have a filter and let people buy/sell energy in sets of 10, 50, and 100?
That way you can spend 3000 crowns on 50 energy after a T1 run and run through most of it again. Or if you just need to get through that last elevator to fight the boss you can buy 10 energy and head on through.
Why limit it to 100? All that does is make it very hard to buy energy because the price of 100 is so expensive, but a lot of times you don't need that much and don't have enough cash. By letting us buy/sell in split chunks, people can buy less energy for crowns they actually have or can reasonably get without needing super skills or 5* gear.
And the market won't be messed up, I doubt anyone would sell 100 energy for 7000 if people can buy 10 energy for 600, it would, usually, all come out to the same price just divided by half or by 10. Plus it can help stabilize, or even reduce, the cost of energy by adding more competition.
u have 70 energy and u know u need 80 energy to do the full run? its your fault u dont have energy in the last elevator