anyone know if they weigh the sauce n lemons in the price?  

100% they will. I’m a butcher to trade and back when I did we used to put paper on scales, you had to pay for that also

Weigh it yourself. Take sauce out weigh it again

If you want just shrimp, get a bag of shrimp, but that is a Shrimp Tray either prepackaged or done in store depending on supplier.

Lemon and sauce are probably also part of the weight, they're included

Yes they are. They charge you shrimp price for lemon