I get why it seems distasteful, but I personally thought it was pretty clever. This site thrives on good, real world examples in the home page, so it would make sense to incentivize people to agree to let the site use their examples. If it were a larger company I would probably not like it either, but I'm willing to give a pass to a very small business.
Maybe there is a lot of value in having lots of samples. People are more likely to give permission to get out of the fee than to get a discount.
Personally I'd increase the discount to around 10% (raising the base price to compensate) and have "Allow us to use this as a sample" checked by default; but I wonder what % of people have a strong reaction like the OP here.
A. Happy to pay the full price!
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Q. Price $117. Can we use this as a sample? (No: +$3)
A. No fucking way I'm paying $3 NOT appear in your gallery of samples!