The biggest difference that hasn't been mentioned is that QTP will do Windows, .NET, Java, Oracle, BPM, better integration with Quality Center, etc. testing where vTest is only for web. That's the reason for the price difference. I wouldn't say that vTest has the same features for less! If you are only doing web testing, then choosing vTest might make more sense, but QTP and vTest are not the same.
And as far as I can tell, vTest is using Javascript injection similar to products like Selenium where QTP manipulates the IE COM object. vTest uses Javascript for the scripting language, QTP uses VBScript.
And as far as I can tell, vTest is using Javascript injection similar to products like Selenium where QTP manipulates the IE COM object. vTest uses Javascript for the scripting language, QTP uses VBScript.