I agree, also if a used cannondale, specialized etc, if upgrading can take the kit off put original front wheel back on and still get half back what you originally paid for the bike and put ekit on the new bike. Does this make sense?The only reason that I would go for a lighter ebike, fitted with a kit, would be to throw it around cross country. They're a nightmare to pedal unassisted.
Without any disrespect to woosh and this is only a question but surely, say a second hand specialized that originally cost £550 must have better frame and components than any off the shelf ebike that cost under £1200?
We can argue wear and tear on a used bike but everything is replaceable and a good frame will outlive me.