In addition, any mage who knows anything about crafting magic items of any sort would also know that the wizard in question had been lying through their teeth about what was involved. If the ring was invented during the era that 2nd edition chronicles, then wizards who delved into item crafting would know that making each ring is a perilous endeavor as you have to know
what exotic materials you need, and then get an adventuring group together to ideally help you survive going to get said exotic materials.
For a Star Ring, maybe it requires ore from a fallen star (meteorite), a vial of blood from a djinn taken in the elemental plane of fire, and a shard harvested from an ice elemental in the elemental plane of ice. Oh, and the hair of a celestial, willingly given, for good measure. If so, the wizard in question might have been more then happy to go through such extremes to protect his girlfriend. But would he be willing to do so over and over again to make dozens of Star Rings? Maybe not, in which case selling the instructions is safer (for the wizard) and more profitable.
If it takes a few hours to do a dozen rings, and you tell people it took three weeks because you had to layer spells properly, how is that taking an inordinately long amount of time to make up the rings in the first place? People will think you NEED a long time to make 'em, but that doesn't mean you actually DO need that much time.
I think you are missing a critical piece of information. It's not "a few hours to do a dozen rings". It's
maybe "three days to two weeks for each ring". And that is if you didn't have to do anything excessively dangerous to get the materials to make each and every ring. One sec, I'll check the actual 3.5 crafting rules real quick. You're not making a dozen rings at once over 4 or 5 hours. You are making a dozen rings
one at a time over however many days it takes (depending on complexity) per ring. So
if it takes only 3 days each, to make a dozen such rings it's literally taking you 36 days of doing likely nothing but eating, sleeping for 8 hours, and working on the ring for 8 hours a day. Because you also had to re-memorize the spells you're casting every day while making the ring.
I just checked the rules, in 3.5 it takes
one day per 1,000 GP base cost of the ring to craft it. So, let's break down how much in 3.5 the Star Ring would cost to make.
*Armor bonus is 1,000 gp squared per bonus, so a +2 bonus is 4,000 gold. Minimum of level 4 to get this armor bonus, will require the Mage Armor spell.
*Save bonus is again 1,000 gp squared per bonus, so a +2 bonus to all saves is (2x3)x(1,000x2), or 6,000 gold. Minimum of level 4 for a +2 bonus each save, 3 saves being improved. Need the Resistance spell, which I believe is a 0 level spell.
*The heat and cold resistance is a Continuous Endure Elements effect, which is a 1st level spell. So that's 2,000xCaster Level. If the creator is a level 4 wizard then this effect will cost 8,000 gold. This cost WILL scale with your wizard's level, so the higher your level the more expensive this is to add.
So total base cost is 4,000+6,000+8,000 gold, or 18,000 gold. This means one single Star Ring takes
eighteen days to craft. Crafting the ring only would cost you 9,000 gold. But you use the base cost to determine how long it takes to craft. So for 18 days you are spending 3 hours studying to re-memorize Mage Armor, Resistance, and Endure Elements. You're spending 8 hours working on the ring. You CAN NOT spend more then 8 hours a day working on the ring, or you'll be forced to start from scratch. Equally you can't work on more then one ring at a time. You're sleeping for 8 hours. Leaving you with 5 hours to do other things each day.
The XP cost for making each ring looks to be 50 xp for every 5 GP. So 180,000 spent to make the ring. So, uhm... Yikes. Don't think that's something anyone's gonna be crafting more then one of at a time. And definitely not at level 4. I suspect the ring was invented
before the rules of magic changed to basically require the wizard to pour bits of themself into every magic item made.
EDIT:
Sorry for the Wall of Info. I fell into Research and Lecture mode. It happens.
EDIT 2:
Double checked XP costs, cause that didn't sound right. it's 1/25th of the base cost in XP. So for a star ring it's 720 xp to craft one ring. Much more reasonable. But still not something a level 4 wizard would want to do too often. Damn SRD with it's confusing layout of info.