Salvage seems to have lots of urban legends about it which are believed by supposedly knowledgeable people.
A first-hand account does not qualify as an urban legend; and I don't think the man that told the story is "supposedly knowledgeable". He has spent his entire life around boats; sailboats in particular and as I mentioned before he was the chairman of SAMS or NAMS at one point (I cant recall which one). If you wish to know who he is; PM me and we can chat more offline about it. If you look carefully at your BoatUS card (if you are a member) the $50 tow is only a rebate on the total bill; not a tow for $50. Many people make that mistake and then get a shockingly high bill because they misunderstood thinking their card is some sort of on the water AAA card.
Read the cases and you'll see that there are a host of factors required to constitute "salvage", and even if met, there are a bunch more factors (called the Blackwall factors from a case with that name) that determine whether the salvor gets big money or pocket change. Low-order salvage may get the claimant no more than a reasonable towage fee. High-order salvage (great peril to saved vessel, costly loss successfully avoided, great risk to salvor's equipment/vessel, great skill by salvor, and the service was voluntarily undertaken, etc).
While this is true; the bigger issue is valuation of the boat VS court costs. If a salvor slaps a lien for the entire value of the boat on it; you are stuck until it is resolved in court. You can't sell the boat and you are going to pay through the nose to have a lawyer defend you. So what happens? The insurance company (assuming you have insurance) usually negotiates a payoff for the salvage lien and then the boat owner gets to keep his boat. I think the valuation of most privately owned pleasure boats does constitute "pocket change" when it comes to courts who regularly deal with valuations above 1 million. I know it sounds strange but a boat worth 80k or less really is not very high dollar in terms of salvage rights.
No peril, no salvage. Just towage. And I doubt whoever provides the tow line makes much difference when both of you have an adequate line available and it's a tossup whose to use.
Another thing that the surveyor said was "never take their line; always provide your own". It does go to the establishment of a salvage right; and in his words it was very important to remember (IIRC it counts toward establishment of the amount of peril you are in). If you can't provide a line to help save yourself; well you are pretty much SOL unless you take the line the salvor is offering.
Many things may constitute maritime liens, at least under federal law. Salvage is one. Repairs are another. So are provisions, launch service, fuel, all kinds of things that are "necessary" to run a vessel that the vessel owner (or charterer, who can run up bills, go broke, and leave owner holding the bag) didn't pay for.
Yes that goes back to when cargo ships, etc were owned by a corporation and the skipper had no money onboard to pay the debts they incurred while traveling to their destination. Every bill was carried as a lien against the boat until the corporation paid the bills. Today it is mostly used as leverage when a dispute arises over payment; not as an IOU as was originally intended. Maritime law is mainly designed for equitable resolution of cases in the shipping industry