You example is an extreme one - the new tax, imposed on vendors alone, is higher than their profit margin. In that case, of course I would not expect them to lose money on every sale.
On the other hand, if that tax is not very high, and the vendor is afraid of raising their prices - maybe demand is low - then yes, I expect them to pay *their* taxes from *their* pocket, just like I pay mY taxes from my wallet.
I'll give you a good example: VAT increased in Portugal sometime ago. Now, VAT is a tax supposed to be paid by costumers. No-one would really expect vendors NOT to raise their prices: they would need to collect some more money from us, to later return it to BigG.
Well, guess what? Because it was a small raise, and economy was already low, some shops did NOT increase their prices. "The VAT increase did not enter our shop", they annouced. Well, of course it did. They simply did not collect that raise from custumers - but BigG will, of course, demand that raise from them. BigG does not care if that raise is being enforced by vendors or not. They just demand to see the money.
So, in order to not raise prices, some vendors were even willing to pay for *some* of their *costumers* taxes.
On the same circunstances, if it was little raise on a tax meant to be paid by vendors, I would expect them to NOT raise their prices.
All in all, it depends on how the economy is going: if vendors feel they would lose business by unfairly raising their prices, and if they feel they have a comfortable profit margin already, they will not. Even if it is a tax NOT meant to be paid by them.
