Your logic is so flawed. First of all a high-end jeweler isn't a market - it's not swarming with people so that the shop is wasting time, but whatever there's a more fundamental flaw with your argument:
If I did go to the blacksmith (game)/ jeweler (irl) and showed them I have 20k gold.
They would instantly show me their best equipment.
And I'd instantly call shenanigans when it was WEIGHTLESS GOLD.
Per my last post: IMMERSION STOPS SOMEWHERE.
I'll support this change when that amount of gold talked about means you need a small truck to carry it ok?
Edit:
Other 'immersion' issues which should be of far more concern to people include:
Swimming in full plate mail - WTF
Carrying 3 suits of armor, 4 battle axes, various HEADS and being able to fight at full efficiency.
Carrying thousands, THOUSANDS of arrows.
That you can function for unlimited days without sleep, food, water or basic hygene.
Outrunning bears/wolves/giants, whilst in full plate. Yes, over 30 mph in FULL PLATE on FOOT.
Seriously, your pockets are TARDIS storage, a bunch of stuff is magically weightless you can manage the impossible an unexplainable and yet and your biggest issue is a vendor won't sell you stuff? Seriously?
Perhaps suspend the suspension of disbelief for just a moment and worry less about it?