inurriing huge shapeshift transaction fee or something else

[ggbtctalk000]

Ok here is the numbers shown on coinomi just before I submitting transaction through shapshift. From zcash to btc conversion the screen shows :

Exchange:
0.643 ZEC @ 558.59 USD

Transaction fee:
0.000180 ZEC @ 0.16 USD

Receive:
0.02516935 BTC @ 428.36 USD

Rounding the fractions and small disregarding small transaction fee for ZEC,
558-428=130$ disappear through thin air? Where did it go?

Is this a another transaction on fee on BTC blockchain? From what I understood shapeshifting involves sending ZEC in this instance to shapeshift's own address and then shapeshift will send me a BITCOIN from their address.

Or this is due to arbitrage?

I think I have moderately good understanding on bitcoin technicals (althought it is wearing out) but I think I will need more time studying on fee calculation I wonder where the good resource on this.

[ggbtctalk000]

looking from shapeshift's website, the bitcoin miner's fee will be is listed as 0.002 which @ today's rate 0.002 * 17000-ish = 34$.