My ViaBTC accelerator experience is the same as mentioned above.
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Even the paid one is not expensive and definitely worth using.
Not expensive?
I've picked a random 1 input 1 output tx from the mempool and this is what the paid service will ask for:
45f8ce98c5c4b9839eec8f6045bfec80d2ea2b863e06622f4cd0d33accdc67f5
Transaction Size (Current TX Size + Previous Unconfirmed TX Size)
141 Bytes = (141 + 0) Bytes
Total fee
0.0021432 BTC ≈ $ 58.10
$58.10 is not expensive?
For a larger tx of 2000 bytes, it's...0.0220192 BTC ≈ $ 596.78 !!!
Never understood what's the point of a transaction accelerator, from the pool's part. They have nothing to gain. It's basically like giving free bitcoin, and as far as the mempool is concerned, 100 transactions for free is rather lots of money.
Promotion, mainly for other services as miners are not really happy about it, see this:
https://bitcointalk.org/index.php?topic=5345553.msg57304026#msg57304026By the way, I don't see them having a size limit. You could create a large transaction, broadcast it and have them accelerated for you? Has anyone tried this?
≤0.5 KB, they are not accepting anything bigger, also over 10sat/b not
vbyte, and not CPFP tx!