Well, the fact that it has been on offer for two weeks without any obvious action means it isn't a steal. If you found the right dealer and the right monthly special, you could probably order one up very similar for $6500 or so new.
For me, buying a used Alembic depends upon how close the specs are to what I really want. I have a similar instrument with a relatively boring vermilion top, but it has a custom neck spec that is narrower than standard. The chances of finding another Alembic on the used market with that neck were pretty slim, so it was worth paying a bit above what I might otherwise have felt the typical price for that model should be.
Is your goal a nice bass, or figuring out exactly what you want in a custom? If the latter, then buying used can be about validating your thoughts so you order the right options. If you have to lose a hundred here or there in the process, it beats making a $10K mistake on a custom. This particular instrument is very vanilla. It has LEDs, which almost everyone who experiences them will tell you is a very useful option. Other than that, it has a pretty top.
To get back to your original question, the price is probably higher than average for the instrument, but similarly featured basses have sold for similar prices in the past. If these are the features you want, then negotiate yourself a deal and don't worry if you pay $3800 for a bass you think is worth $3500. If you're just looking for an Alembic at the best price, you may be able to do better. Read recent archives of the for sale boards here to get an idea of what has been offered and at what prices.
If you pay a high price and then decide the instrument doesn't work for you, you will certainly be unhappy if you lose a few hundred on the sale two months later. On the other hand, after you've bonded with the instrument and decided it's a keeper, a little extra money won't matter.
