I don't think so. They're still making the exact same revenue per sale on average. The cost isn't relevant here, another way of looking at it is in the case the customer pays nothing they've lost the cost of the goods and the profit they would have otherwise made, so it evens out.

It works out well for the seller if, by providing the option to gamble on the product, they increase sales, which I would guess it would (at the expense of being morally grey).

This would be a winning strategy for the seller given that the value of the product is less than what they charge.

Yes! Yes, indeed!

Nah it works out the exact same. Say you make $10 every time you sell a $100 product. That means you have a 50/50 chance of either gaining $110 or losing $90. 110*0.5 + (-90)*0.5 = $10.

It also takes one potential guaranteed buyer off the market, the value is whatever people are willing to pay for it meaning they would be losing the exact amount of value they were changing.