Me thinks this seller is trying to use postage to lift up his profit margin.

No, actually what is happening is that the seller is using the item price of the Buy It Now,to subsidise the postage price. Do you realise that only a letter can be posted for $3.00?

Why do YOU care how the price is made up? Why do you care how, what and why the seller makes profit. Profit is profit, they cannot afford to sell stuff if they lose money on it.

I think that somebody is focussing on things that are not important. You are being given a choice, and it's up to you to choose what price structure you prefer. To me, and every other buyer who owns a calculator, the $15.98 is $4 cheaper.

Would you prefer to pay $20.99 with FREE Postage?

How about I buy the one for $4.99 + $10.99 postage, and then make a Buy It Now just for you? Of course, I'll need to make a profit so let's make it $20.99 in total. Please inform me of your preferred cost breakdown of Item and Postage so I can set it up for you.