The game is currently perfectly priced for what it offers in my opinion.  I'll give anyone about 8 hours of great fun, afterward the replayability is limited. Which is totally reasonable at this price point, I didn't expect it any other way.

One way to greatly increase the replayability (and price) would be to randomize the recipes on each run, perhaps in one run for example the planet has no blueshrooms, but it has spice requiring a tool to extract and a machine to process so it can be used. You're used to be able to cook up a hearthy meal with the same 3 ingredients but now the recipe has changed and is harder to do. The reverse could also apply where in some runs you find a few metal sheets lying around which just need to be collected. You wouldn't need many additional assets, the main difference would be that each time you play you won't know what the recipes will be until you actually do the research. But I understand that it's a lot of work, it's only a suggestion.

Randomizing the price of tech upgrades would also be easy to implement, if cooking requires 15 samples the run will go very differently.

I don't think the game needs to be much more difficult as long as each run has its own small challenges which aren't exactly the same as what you faced before.

One way to increase easily the difficulty & challenge of the game (without resources sliders for each resources type, that could be hard to code if all is well balanced/interdependent in the code, like discussed in the topic here : https://itch.io/t/851355/mewnbase-difficulty ) could be to have a simple "x2", "x3",  (etc...) difficulty option for the recipes (doubling the necessary ingredients for a recipe, for the x2 option obviously!). Should be easy enough to code i think, and make a difference for the players searching for a challenge! (that way it increased the gameplay ever more,  without deteriorating the relative balance of all things!)