the yvUSD market is a great showcase of how a Flex market matures
~600k USDC of liquidity seems large enough for real competition between loopers to emerge
utilization reaches 100% quickly, but the avg borrow rate starts low
over time, loopers redeem each other and the avg rate rises until the market finds its clearing price and starts to stabilize
in this case, loopers seem to target ~15% APY
with yvUSD earning ~6.2%, they can afford to pay around 5% to borrow
and because Flex runs @ 100% util, lenders earn that full ~5% -- no idle liquidity drag (at 90% util, they'd earn ~4.5%)
looking at similar loops elsewhere (eg siUSD on Morpho), there still seems to be room for borrow rates to move higher
as the market grows and larger loopers enter, that should happen naturally