There's no demand for those coins. $PAC may have a $5M market cap, but it had $6,500 in volume in the last 24 hours. Some (most?) of that volume is likely to be people just moving stuff around rather than actual buying/selling between people.
You might get rich on paper, but good luck getting anyone to help you convert your riches into spendable currency.
The thing is, the amount of GPU processing power required to attack Ethereum is not readily available, and certainly not at a cost of only $106k. That $106k figure comes from extrapolating out marginal rental cost of a single GPU, never mind that there aren't enough GPUs rental to overwhelm the whole network.
To give you an idea, the overall Ethereum network is currently 190 PH/s, so you'd need significantly more than that to have a high chance of launching a short term attack with reasonable success rate (if you only control 51% then your odds actually aren't great). Let's say you need 300 PH/s.
Well, the average modern AMD graphics card that is suitable for mining Ethereum only does around 30 MH/s. That means that you need 10 million such graphics cards. They simply aren't available for rental anywhere at such scale.
That's why you're not seeing such an attack happening. The raw monetary figures are misleading.
You might get rich on paper, but good luck getting anyone to help you convert your riches into spendable currency.