According to your percentagesm my 130k NT players for example should bring 25-30k in merchandise bonuses each, but they dont. The percentages, as i see them, are more like 10% for own nationality players and around 7% for foreign nationality NT players.
Don't know where you got your data from, but I did a study on my 280k NT player. Although there was only one sample, but I guess it's pretty much gives us the idea of how much you will earn from a NT player.
When I had my NT player, I was earning around 150k a week in merchandise alone. After selling him, my merchandise halved, to 70k. This means he was bagging me 70k+ worth of merchandise money each week, which is close to 30%.
One of our local teams bought him some time later, and due to my curiosity, I asked for their merchandise change. It went from 40k a week to close to 100k a week. That's around 40k to 50k increase, and is close to 20%.
I haven't looked into other NT players yet, but if you can supply me with your data, I'll be glad to consider it as well.
In my experience you are both kind of right

. My foreign NT-player Egon Olesen (about 250k salary) has a nice influence on my merchandise. When he plays for the national team my merchandise increases by about 10k (Xsagos number). But if you consider that my merchandise is already higher just for having a very good player on my team the merchandise increases quite a lot as well. So if you add that it might be close to 30k (rough estimate since I bought him a long time ago).
But yeah the increase just for him playing on the National team seems around 10k-15k to me.
Crunchy! If you eat fast enough