” is it an aspect of Spanish culture which I will need to understand “
Like all markets the right price is what one is will to accept & other is willing to offer. So this is an aspect of the Spanish culture you don’t need to worry about.
“maybe a third or more under the asking price? “
You are perfectly entitled to make what ever offer you wish, like in UK. The Spanish can become very sensitive if the offer is too low & further will not take you seriously. Besides they can also get very stubborn and irrational & just wont do business with you. The thinking behind the stubbornness cannot be generalized.
“Unlike one’s main home, nobody has to buy a holiday home.”
Not all buyers are buying as holiday homes. Spaniards, buying to live there upgrading/downgrading etc or for their parents. Spaniard also know that if you are buying as holiday home than you either have cash or capacity to raise cash. They also know that give Englishman sunshine & they are yours.
I hope it helps. Finally it is a mistake to compare the very mature English property market with a evolving Spanish market towards a maturity. This was before the current crises. Besides the market is very fragmented and each town & city has its macro market. l
And whilst most sensible folk are happy to negotiate a price when we’re talking about a bracket of 10% or so, this sort of discrepancy unsettles most people. So how will this market unlock?