Depending on which alchemy items you're referring to, your statement may be incorrect.
Most alchemy items that come from caches (
full list here) are unavailible in the marketplace simply because it's easier to sell the unopened caches as you can now choose what component you want to get from them. So technically the supply of these items are a lot higher than they were before, you're just not looking in the right place.
However, there are some items only availible through the marketplace (mostly ones won through old RIGs) that are becoming more and more scarce. A small number still appear with every new RIG, but not as many as are needed or taken out of the system due to items being crafted.
Also, some replenishable items (items won from games, zOMG loot items) are also becoming scarce, but this isn't really an issue since there's always more to be found.
So, until they fix this issue, I suggest using recipes that don't require too many of the "marketplace-only" items. Alchemy is still quite usable with the proper research.