Why to pay them? It is free to use.
not all transactions are free
Now you can submit your "upto 400 byte" size transactions for free.
while it's true there is no such thing as free lunch
paying the $4 for tx > 400 bytes to accelerate your tx with confirmTX is totally useless... scam
he wrote script and used the available free accelerator out there and charged you a fee
and he simply just return the fee if the accelaration failed within time limit (he bets on fail/success chance)
it seems he got choked on tx fee for refunding all failed txs and decided to keep the fee and run away
he depended on someone's service for including the tx in blockchain and in no way in control any of it
if he is affiliated or is directly accelerate txs himself using his own resources it would have been understandable
you would be better to just pay/donate directly to ViaBTC who mines the block