"Maybe I'm just too close to the situation and being unreasonable." --- Absolutely not !!!!!
If you have bought from this guy before, I'd like to think he'd accept your offer, or counter with something very close. I certainly would, because "I" want "you" as a future customer. Not only for that "$100" card, but potentially (since you now are happy with me), many more "$100" cards, as well as, higher value cards.
Even if you had not bought from him before, the same would apply, as in hope of future business.
I wouldn't be a jerk, and tell him to kiss off, just decline and move on. There are many "reasonable" sellers* out there, that would gladly help you out.
Scott
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