I too was lured in by the integration aspect... but in retrospect the reason I thought I needed the integration was because of the horrible user interface most synths that were created over the last 25 years offered. Since then, synth makers have realized how important the experience of the knobs on the panel is, and the designs have gotten better. Basically they improved by working more like synths from the 1970's did
.... A good set of knobs is WAY superior to DAW integration.
Meanwhile, some vendors like Roland seem to be doing a better job with integration (albeit a different way via the plugout technology), but at the end of the day the Roland stuff is still digital and doesn't compete with Sequential IMO.
Since $4,300 indicates you're referring to the Prophet 10, I think I can solve that riddle for ya
....
1. A vintage Prophet 10 is about $15,000, while a new one is $4,300.... slight cost savings there
2. A new Prophet 10 comes with a warranty, and even outside the warranty Sequential's policy is to fix any future issue for flat fee of $25... they have the best customer service in the industry and its all made in USA
3. The original Prophet 10 had issues with stability due to overheating which are fully resolved with the newer unit
4. You're getting 10 voices of VCO polyphony... nearest competitor on full spec would be the Moog one with 8 voices for $6,500
5. Not only all of those voices, but you get a switch that toggles between the two filter types of the original Prophet Rev 1/2 or the Rev 3, something that vintage units cannot do! And remember, vintage units cost more
6. Dude! it's an authentic freaking Prophet!!! ..... a faithful recreation of what is probably the most important synthesizer in existence, all for about the same price as a well equipped iMac would cost.
7. As far as "dated" sound, vintage analog is very sought after because it sounds richer than the thin digital modern sound. But remember when you hear a Prophet 5/10 most people are demoing it without FX (because it doesn't have any built in). Most "modern" sound comes from digital FX, so if you want to modernize the digital tone you have to bring your own FX pedals or plugins.
This is just some of the reasons why there is an endless list of synthheads waiting for their backordered unit, and some of them I'm sure could very quickly chime in with a few dozen reasons of their own.