Three productized tiers — €500 for a thorough visit, €950 to do the trip together, €1,500+ for full pre-signing diligence. Add a Tinsa appraisal, structural survey, legal title check or anything else you need à la carte. Everything priced transparently up front.
You spotted an interesting listing on Idealista but flying down would be premature. You want one informed walk-through before deciding whether to go further.