You won't need your ear measured because they are not custom in ear monitors (CIEM).  With CIEM's there are a couple ways to do it but the easiest would be to go to an audiologist and have them take an impression.  You would then send that impression to the lab of the CIEM manufacturer.   Check...

W30's are not custom fit unless you consider having a dozen different foam or silicone plugs to go in your ears "custom fit".   No impressions are required.  However, they do fit well.    Crutchfield is an authorized reseller and they have them in stock.  

I have a really hard time trusting anything on eBay that comes from Hong Kong.  Occasionally you can get legit stuff but it is hard to know.  The price does not seem too far off so my guess would be that they are legitimate, however they are most likely grey market.  Sennheiser does not warranty...

You looking for CIEM's or just standard IEM's?  While I would not consider them super bass headphones I really like the Westone W30's for standard IEM's.  They are at the upper end of your price range but I was blown away on not only the amount of sound but also quality compared to the se215's...

I'm new to the forum but no stranger to hi-fi audio.  Have been lurking around Head-fi for about a year but just finally registered.     A while back I decided to go the cheap route and purchase a pair of W30's off of eBay.  The guy was fairly close to me, had reasonable feedback and the only...