Hmm...doesn't seem all that thoughtful if Ken is the one putting in all the work to get the scent onto the paper. Not like it's something that requires years of training to pull off either. Nobutada could have had Ken teach him and then he could have repeated the process by himself for a month or so.
Sure, they probably pay Ken well, but that's not really his main job and it doesn't seem like Nobutada is giving him a reward for this. The gift is also not something super expensive to acquire. So, it's not like Nobutada could boast that he gave up a lot of his own wealth/assets to convey his feelings. Nobutada didn't even come up with the idea either. And Ken was already there, hired by his father years ago. Nobutada can't even claim that he searched high and low to find a talented man to help him do this.
This might as well be the equivalent of a regular guy in modern times writing a shitty poem, spraying the paper with some cheap perfume, throwing it into a postal service mail box, and calling it a day.
Seems like Ken spends more effort doing these sort of stuff for his bosses than for Natsu. Other than the comb and the occasional souvenir, I can't really remember the last time he did something special for Natsu. I'm sure he does it off screen, but can't the Mangaka show at least one panel where he's giving her some flowers or something from time to time? Nope. They just show him going home like usual, seeing Natsu, and smiling. Just smiling....(Not even menacingly. At least, that would have been interesting.)