I don't see anything wrong with it. A few people have done that with my modules and I just kinda laughed it off because somewhere, someone WILL pay the extra money. I've done it.
From this forum, I bought a MrScary and TopBoost for $205. Months later, I sold the Top Boost for $125 and the MrScary for $185. This may be different because my intent wasn't to make money. I actually wanted those modules, but they ended up redundant with modules I already had.