I had this same conundrum come up in our TOR group when we started worrying about TP = 1 gold. Initially I almost house-ruled that instead 12TP = 1 encumbrance, because that's a nice round year's worth of prosperous living.
But then I remembered that encumbrance is NOT simply weight. It is the awkwardness and unwieldiness of things. A great spear isn't 4 enc because it simply weighs so much, it's because it's a 9+ foot long pole that you're trying to carry through Mirkwood.
So going off it not being too heavy to carry, I started wondering why it has such a high encumbrance? Simply put, value.
Someone had mentioned that Smaug's hoard is huge, so they don't think that precious metals are uncommon in Middle Earth. But that's like saying "We've seen the 4500 metric tons of gold stored at Ft. Knox, gold must not be that rare."
If I had ONE, 1oz gold coin on me, modern value has that priced at ~$1200 currently. In-game we know that 1TP is enough to sustain you for a whole month at a prosperous standard of living. That's a lot of money in my opinion, and if a character had a bag of ten gold pieces on him I would suspect that he is freaking the crap out right now making sure he doesn't drop it or lose it, or that no one else in the fellowship is eyeing to steal it.
It could consume his thoughts on every river crossing, every bump while riding a pony, during combat when he thought he felt the pouch fall. It could very well be a source of corruption (or anguish if he did lose that much money). That's how I see it.
Granted we don't always play that "oh you found a small pouch of silver, KEEP TRACK, add encumbrance, etc, etc." But if my players found a small troll hoard of a few hundred treasure points I'd sure question how they plan to transport that back to a sanctuary (for it to be invested or what have you). This is why I feel that Francesco had it right that 1 gold coin = 1 treasure point = 1 encumbrance... more or less.
