As part of a recent release, the number of recipes that can be bought from Basil was limited to one copy per player per terminal.

While I can almost understand the desire for a vague limit, I'd like to make a few points in hopes of convincing interested parties that one copy per player is far too low a limit. The short version: please either abolish vendor purchase limits, or raise them to a more realistic cap of 3-4 copies per player. Giving vendors larger inventories would also help: I've seen some vendors that sell only 7-8 recipes at a time, while others sell 22.

Some reasons are listed below.

1. This is a social game- this is not the most important point, but I'm putting it first as a disclaimer: I sell a lot of recipes. In addition to the fun that can be had wherever a player economy exists, playing with your friends often requires ensuring that they, too, have good gear. Being able to pick up 2-3 extra copies of a good recipe helps to build the social aspects of the game.
2. There are other barriers to crafting- Just signing up and buying recipes will get you nowhere; you also need energy, materials, and heat. The latter can not be purchased, and many 4* items take a week or more of casual play to level up. Just selling recipes does not make players instant supermen; it just reduces the artificial grind, and encourages people to make a wider variety of items.
3. New players aren't the target market- To follow up on the last point: if this change was meant to keep new players from getting an early advantage, it's worth noting that very few of my customers (less than 15%) are new players with energy-fueled riches. Most recipe buyers are experienced players with a clear idea of what they want to make. They want to experiment, and they want to spend energy crafting expensive things... if the recipe system will let them.
4. Finding recipes is a painful experience*- For the past three weeks, I've had half a dozen friends on the lookout for the Volcanic Demo Suit. None of us have found it, despite hundreds to thousands of energy units spent on runs to tier 3 terminals. There is a very good reason why spare copies of recipes are valuable.
5. The value of one recipe depends on the availability of others- Items like the 2* vaporizer bomb are useful only for their upgrade potential. This means that I am far more likely to buy a recipe if I think that the other pieces can be found in a reasonable timeframe. (say, 1-2 weeks of my own gameplay) A healthy recipe resale market encourages crafting (and reduces grind) by helping people to find the missing links in the chain.

* Here's a homework question for the stats-minded among you: as the number of tier 3 runs increases, you should asymptotically encounter the full list of possible recipes. How many runs does it require to see 95% of all 4-5* recipes? I'd suspect the answer is much higher than you'd expect from #possible recipes/avg vendor inventory size.... and that would be true even if inventory size were increased.