@Thrawn-
I didn't really set up my query well. I completely agree with you that the Heroes max out on gold coin equipment too early. I meant to question Quest 8 of the Game System because my math doesn't agree. Let me explain:
Quests 1-8 Gold Coin Special Treasure
Q1: 204 / Q2: 240+60 / Q3: 180+24 / Q4: 240 / Q5: 144 / Q6: 0 / Q7: 400 / Q8: 400+150
Adding these together, the special treasure total for the first 8 Quests works out to 2,042 gold coins.
The bold amounts are those actually found in chests, rather than the others which are rewards. However, chests are not always successfully found by most groups. (Perhaps the group felt like finishing early rather than doing a thorough explore, or they were too weak to continue.) I'd suggest it's reasonable to assume 25% of those chests go undiscovered. That would reduce the 582 gold coins from chests downward by an amount of 146 GCs. This, in turn reduces the original 2,042 GC total down to 1,896 GCs.
Of course, Treasure Card deck gold coin treasure has to be added in. My original assumption was that most players stop looting the (N. Amer.) Treasure Card deck when the odds are 2 to 1 against for a beneficial card. That would stop draws after just 4 beneficial cards had been pulled, but that didn't match what happened in our games. Those Potions of Healing drive the looting, in my experience, as they are far and away the most valuable resource in the deck. So looking at the card distribution of 6 potions (2 sets of 3), 8 GC treasure including gems (2 sets of 4), and 10 detrimental, pulling 7 beneficial cards would account for 1 set of potion cards (including 1 Potion of Healing) and 1 set of GC treasure cards. The last successful pull would be at 4 to 9 odds of drawing a beneficial card vs. a detrimental one--not far at all past 2 to 1 psychology.
So, as a side-effect of efficiently looting for Potions of Healing, one set of monetary treasure cards worth 125 GCs is gotten by a group of Heroes every Quest (on average, of course). Eight Quests would yield an even 1,000 GCs. Add that to the special treasure total of 1896 and that group of Heroes should have 2896 GCs to spend on equipment. Pretty darn close to your total of 2916! I thought things would work out differently, but I changed some things as I studied the problem tonight, such as 7 draws instead of 5, and only reducing the chest treasure by 25%, not all special treasure. Glad you brought up the issue.

Did you have a different method to arrive at your number?
It's a niggle, but your equipment totals don't quite fit. I come up with a total cost of 2,925 GCs. That would mean coming up shy another item, probably a Crossbow, Battle Axe, or Chain Mail, as the cheaper ones are bought first. Quest 9 will take care of that with 200 GCs to be found in chests there (even if it's reduced to 150 GCs by my 25% rule).
Where we differ is what constitutes a max-out. I'd upgrade the Broadswords to Longswords or Battle Axes, so 1 of each there (what Hero would be satisfied with less?). That's another 800 GCs. Don't forget Daggers for the Wizard, say 2 per Quest, starting with Quest 2. That's infinite, but just count to the max-out. I think you could also include Tool Kits at 250 GCs a pop for the three non-Dwarf Heroes as part of the max out. (What if the Dwarf dies mid-Quest, or a Hero becomes separated?) That's another 750 GCs needed. Add in that Plate Mail at 850 GCs or another Chain Mail and either 2,400 or 2,050 GCs are still needed. Altogether, that's 5,325 or 4,975 GCs needed for the Heroes to glut out on the Armory items (not including Daggers).
All 14 Quests will yield 4,543 GCs using my methods of calculation. That's not enough to reach either max-out that I described. So starting at Quest 2, Daggers will be used throughout the Game System Quests at a cost of 650 GCs. Added in, the new max-out totals are 5,975 or 5,625 GCs. Kellar's Keep will have to provide the max-out I see. Not until Quest 8 is the 1,900 GCs available from found special treasure and Treasure Cards to raise the necessary total to 6,443 GCs. By then, the additional Dagger costs will total 400 GCs, raising the max-out costs to 6,375 or 6,025 GCs. The Armory is finally bought out (but for Daggers) with 68 or 418 GCs remaining, depending if Chain Mail or Plate Mail is chosen for the third Hero.
Of course, this is just how I see things--there are some judgments that can change the numbers: aggressive or hesitant Treasure Card drawing, preferences for a satisfying buy-out for a Hero, and tenacity in searching for special treasure all can affect the max-out. Don't forget Hero Death--maybe nobody was present to stop a victorious monster from looting all of his items and treasure. There's also the option of selling back equipment for half value from the Elf and Barbarian Quest Packs--one I plan to use. All these variables can slide the numbers quite a bit. Still, I'm going with Kellar's Keep, Quest 8 as the milestone where the use of Gold Coins dramatically changes.
I'm gonna say it again--you're right that Hero Quest stales as far as character progression goes once max-out is reached. You point out an important issue that deserves attention from the community. I don't mean to contradict your view, rather my intent is to broaden it with another opinion. I look forward to more of your analysis of play shortcomings. I feel this may have came off as too pedantic or contradictory, but I enjoyed the analysis process. This kind of thread is what attracted me to the Inn in the first place.