They may have missed their chance to cash in on Salah for anything like £100-150m. Is anyone really likely to pay that sort of money for him in the current environment? Last year the Saudi League threw money around and players were willing to take it thinking "how bad could it be?". It's not guaranteed that this year will be the same. The league is poor quality, the attendances are pitiful, the lifestyle is terrible for players and their families, especially compared to the lives they are used to living. The PIF may look at it as a gamble that won't pay off and concentrate on other things. It could all become another distant memory like the Chinese Super League.
Salah might prefer to see out the last year of his contract and go on a free to someone like PSG for a couple of years.