I think it's hard to gouge in pinball because pinball is not a necessity. It just isn't. You won't die and your general welfare won't degrade. It's a completely optional purchase, and the market of your fellow hobbyists will establish a going rate whereby prices will trend accordingly. Not every purchase can resell at a profit.
As far as "profiting" a matter of personal conscience, I've only sold 3 games. One at market, one probably below, and the other probably high. But in all cases I fielded lots of interest and both sides were happy and comfortable, I made a "profit" but felt I had earned it since I took on the risk of project games and spent a fair amount of time on time. No worries... and the one I sold low, eh... I got it really cheap so for karma's sake I passed a deal on, but still made a fair profit on my efforts.
Anyway, I've no issue with folks asking whatever they like for a game. People will either buy it, or move on... and eventually moonshot askers may see the light and lower to where it finally sells.
What is NOT OK is high askers who are complete d-bags, such as this post for an example of near-gouging and how NOT to do it: