Your DATAassist 2 is expensive, it is afterall an extension and not the price of dreamweaver. Also, where are your videos to this?
I look forward to hearing from you. Dreameaver upgrades are only US$399. For this it is a full bodied software.
Market size and demand drive product prices. WebAssist extension sales will only be a tiny fraction of dreamweaver sales.
If 50,000 people buy dreamweaver then adobe can make a profit charging small amounts. If only 100 people buy data assist then of course the price must be higher to cover development costs.
You can subscribe for a fairly low monthly amount and get all the extensions if you want.