I have tried both sides of this. As in I have done selling paste and selling stims. Here is my experience. Paste will fetch you 8k per paste. Stims will fetch you 15-19k. If you find your own paste, I do not see the reason why not to craft into stim.
From what I find. Unless you have a mission discovery. It takes about 4 missions to find 3 paste. My sample size will be crafting 3 times. So you will need 12 paste as it is 4 per craft. 12@8k is 96k. Where is you convert to stim it becomes 9 stims in worst case (chance to crit) 9@15k is 135k.
40k difference. So even if you do buy it @ 8k you still make 40k.
I do not see how selling paste will every make more money than stims.
P.s. lately stims have been selling for 18k on my server. Also crits are free money. Where you have to crit to get paste. But hey if I can't keep up with demand I will buy paste.
Same goes for 27 armorings if you crit that's like a free million credits.
Remember the Bioanalysis materials - gather or buy - in your profit figuring.
Then factor in the time to make and post and repost and repost and repost stims... because EVERYONE is making them and you're undercut within 30 minutes... Very not worth it. Very.