Coventry sold the Sweden striker to Sporting two years ago for €24m.
Gyokeres is now being linked with the likes of Manchester United, Newcastle and Arsenal.
King told CoventryLive: "Listen, the deal we made with Viktor was a difficult deal to get done. He was going to Sporting Lisbon, Sporting Lisbon, Sporting Lisbon or Sporting Lisbon and they felt they were going to get what they wanted and we had to fight hard to get our deal.
"And the deal we got I thought was pretty good considering he har.r," he tells CoventryLive and continues:
"I was happy with the deal and if he is sold on for 100 million euros, we get some money to put in the coffers. He has obviously been successful, which shows what he did for us in that 22/23 season where we really played transitional football, and if he had been injured in the second half of the season... I was more worried about relegation (from Championship), to be honest.
"I was happy with the deal and if he is sold on for 100 million euros, we get some money to put in the coffers. We have already invested a lot of money in this club."