I ordered a new 55W HID kit from ddmtuning but the ballasts clearly say "Power Out=35W" Is this a mistake or did I get ripped off

 

Sounds like the wrong kit..be careful with DDM..from other posts here it sounds like they are ceasing selling HID kits very soon. So...no warranties !! I don't know this for a fact though..just be careful.

 

Yes, the ballasts control the output, so you should have received 55W ballasts.

 

Could be both. There are only a very few true 50W ballast makers in the world. I could name all of them on my hands. 99/100 times the "55W" or even "75W" output claims on most eBay sites are false. IIRC DDM is one of the few who actually output 48W (claimed 55W) but they are going out of business. Call them first and just see if it was a shipping problem.