For me, for annual vegetables, it depends on how expensive they were. I'd like to supply an "eatable" amount, but that can get expensive, for example with beans.
If enough seeds for direct-seeding a 5-10 foot row cost me less than, say 40-60 cents, and I got a big enough packet to make more than 6 trade packets, I'll do that. That goal is to supply someone who wants to eat it for many meals. Say a $5 bulk packet divided 10 ways.
(Note that a $2.50 packet will seldom be big enough to divide 5 ways. Big year-end packets can be a great deal!)
Once I got a whole OUNCE of lettuce seeds inexpensively, so I made some TEASPOON-size packets, which I think would supply most people for several years. That was based on "these are very affordable".
But if the seeds are more expensive, and 50-60-cents-worth only make a "sample size", say 30-50 seeds, I'll make up smaller packets like that. More than enough for someone to TRY the variety to see if they like it. If they want to make more servings, they would have to start in cells and transplant, instead of direct sowing and thinning.
Recently I got some seeds in a much smaller packet than I expected, so that 27 hybrid squash seeds turned out to cost $4. Before then, "20 seeds" was my bare minimum size to trade, but I stretched a point so I could make two trade packets instead of just one, $4 trade packet. Hopefully, squash make such big plants that it was a "fair" size.
So my packets usually vary between 40 and 400 seeds, depending mainly on my cost.
If they will have low germination, more seeds.
If it's a perennial and they only need a few plants to establish the "patch", fewer.
Self-saved, it depends on how many I have. If I have a cup of seed, I'll divide it into teaspoons or tablespoons. If I only have a pinch, I'll make up some pkts with mini-pinches.