I believe you are reffering to Sandelving Aviation Supply in Germany, aka Aircraft Spruce Europe.
Well, AS USA is cheaper but not so much after you paid the import VAT and shipping.
Also, IME, AS USA equally don’t supply an 8130-3 in most cases. They make you tick a box confirming you are aware of their policy on this.
It doesn’t bother N-reg owners (well unless they have an anally retarded A&P ) because for most smaller parts an A&P has the authority to declare a part as airworthy upon being satisfied of its origin, etc, but EASA-reg people have a more complicated situation.
Maybe below 1200kg (ELA1) it is different? Some years ago I wrote this article which documented what most people didn’t know back then.
I picked up this old thread to continue this.
The other company I use for bits is LAS but they tend to not stock the less common items.
LAS are good for very small quantity’s and Adams are good on price but you may have to wait a bit.
All round Airpart Suply are probably the best for most items.
Just wanted to pop a data point in here for Saywell. I just got an RG-35AXC for £280 which is a good £80 cheaper than I could find elsewhere online. They’re €475 on Aircraft Spruce EU!