The second one is a scenario like we were talking about with the tickets. You would be owed the agreed upon price, regardless if your markup was 10% or 1000%. If the intent all along was not to pay for the widgets then you can forcefully go get the money from them or property where the value adds up to that price (used widgets are worth less than new ones, so you would be entitled to more than just getting the widgets back). If some other situation came up and they couldn't pay, then maybe they have a performance bond like you mentioned or maybe an arbitrator would rule and place a lien on their property or something.
The third scenario I would think you would only have a claim to the cost of the widget and not the mark up, since they didn't benefit from the transaction either. You would have to have a solid agreement to purchase the item though. If you just ordered it hoping they would buy it then you don't have a claim to anything.
Regardless, to answer the OP, there is no scenario where you can lock someone in a cage in lieu of repayment.