I was wondering why doesn't the 55 year old experienced sailor you have take on the role of skipper for this trip.
You are looking at a voyage of over 1500 sea miles and taking a month or so in time ... you expect to attract a skipper and expect him to contribute between 150 and 300 Euro. Hmmm even at my low rates quoted below I would require $3000 AU on the mile rate and the voyage would be considerably less than 30 days or $6000 on the day rate, plus of course airfares etc.
I know you are looking at a trip in Asis and not Australia but the below information may be a good indicator for you.
As a delivery skipper I usually charge $2 Au per nautical mile plus airfares and onboard expenses, (basic food etc), days in Port or days spent on repairs etc are usually in addition to the mile rate as well . Alternatively its $200 per day for the skipper and $100 per day for each crew member I provide. There also needs to be financial provision for when things go wrong, cost of breakdown or gear failures etc during the trip. I have delivered yachts from Darwin, Cairns, the Whitsundays etc to various points in Australia for the past 20 plus years.
I also at times skipper locally for others at a rate of $160 per day.
I agree that a skipper is totally responsible for the vessel, crew and any legalities arising from its operation and I would not agree to sail someone else's yacht on what seems to be a delivery without reasonable remuneration.
The cost of vessel delivery depends on many variables such as ...
The size of the vessel and it's condition
The length and challenges of the trip
The technological and mechanical complexity, or lack thereof, of the vessel
The number of crew required
The amount of pre- and post-delivery management required
Pre-trip survey, slipping if required for repairs or installation of equipment, anti-fouling etc
... all need to be considered and discussed.
Contracts for cruiser or yacht delivery on a per-mile basis is generally by negotiation as are daily rates. A major factor effecting per-mile rates for delivery is the journey itself, to use the Panama Canal as an example, transit allocations may vary by days.
Typical industry rates for local coastal deliveries in Australia runs from around $300 a day for a skipper, and $150 a day for crew, alternatively the per mile rate is about $3.50 per nautical mile. Obviously this will increase as higher qualifications are required.
Hope this gives you some food for thought.
"No matter where you go, there you are".