Now with these:
1. How much is this product with tax? (How come I hear this a lot? Is this correct?)
2. How much is this product with taxes? (I don't here 'taxes' a lot? Is this correct?)
Unfortunately, I hear #2 more often than #1. We have provincial sales tax (PST) and government sales tax (GST) on almost everything we buy. It's still quite common to use #1, even though we know we mean both provincial and government tax.