Also the transaction looks like a very large transaction in size and viabtc has limit of 500KB.
0.5 KB! 500kb is half a block.
I am seeing $ $721.46 and $2,979 respectively. Does this vary, every second the state of the mempool changes?
It's just an estimator and of course it does, imagine somebody is dumping half a block of tx with 300sat/vb, if you keep your acceleration fees at 100sat/vb you're losing money by including that!
Also that fee on mempool is quite tricky, you need to read the thing carefully:
Choose the maximum extra transaction fee you're willing to pay to get into the next block.
If the estimated next block rate rises beyond this limit, we will automatically cancel your acceleration request.
So if in the last moment there is a spike, you might end being charged the maximum you have selected, so not 127 sat/vB as I type now but 242sat/vb.
And you won't be able to initiate an acceleration unless you have the money for the 242sat/vb fee.
Do miners even get a share of that highly charged USDT amount?
Nope, miners get screwed twice with accelerators
- they include free tx with lower fee, so lower income for miners
- they keep all the paid accelerators fees for themselves, while we get the initial fee for that tx that underpaid for that block space