Lennon hailed Hooper as Celtic's best striker since Henrik Larsson after the Englishman returned south to sign for Norwich.
Like Larsson, who scored 242 goals for Celtic after signing from Feyenoord for £650,000, Hooper more than justified his price tag.
The 25-year-old netted 82 goals in three years following his £2.4million move from Scunthorpe before earning Celtic more than double their initial outlay.
And it is that imaginative and potentially lucrative signing policy that Celtic will continue to deploy, despite bringing in almost £18million in the past few weeks.
Victor Wanyama's signing was even more profitable with his initial fee of £900,000 dwarfed by the £12.5million it took for the club to sell him to Southampton two years later.
But the re-sale value is only one consideration when Celtic enter the transfer market as Lennon does not want to bring in a player on much higher wages than those who got the club to the last 16 of the Champions League last season.
Lennon, who has brought in Virgil van Dijk, Amido Balde and free agent Steven Mouyokolo for a total of about £5million, said: "We're looking and looking, it's not as easy as everyone thinks.
"Yes, we have brought in a lot of money but we have to safeguard the future of the club as well.
"We have to be mindful of that when we go into negotiations with players. Some of the prices are too much, some of the wages are too much and sometimes players are happy where they are.
"We are trying to push the button on one or two players. We have already brought three in but obviously attacking areas are a priority."
Lennon gave little away on whether he would return for Wolves striker Kevin Doyle following a failed attempt to sign the Irishman in January.
He confirmed he had watched Evian striker Saber Khelifa and that the Tunisian was an option, but added that he had a "list as long as your arm".
With the second of three potential Champions League qualifiers beginning next week against Swedish side Elfsborg, Lennon would naturally like a forward in quickly to boost his team's options of reaching the group stages.
But he said: "Listen, we have been trying to get a striker in for three or four months. It's not as easily achieved as some people think.
"I don't think we are going to spend six or seven million pounds on a player - I'm not going to break a spirit and wage structure here because once you start doing that, I'll be getting a lot of knocks on the door.
"Everyone talks about a marquee signing. Players who cost six or seven million pounds are difficult to attract.
"In Gary's case we couldn't offer him the same sort of package as Norwich. That's just the reality of where we are at the minute.
"If we can consistently get Champions League football over the next four or five years, that outlook might change, but the days of competing with Premier League clubs for fees and wages are not here at the minute anyway."
Lennon has the likes of Anthony Stokes, Balde, Georgios Samaras and Tony Watt competing for a centre-forward role but Hooper has been his top scorer for the last three seasons.
"For me he is one of my best signings in so many ways - value for money, the improvement in the player, his goals obviously, the link-up play.
"I think he has been the best striker here since Henrik and he will be a huge loss to us but we move on.
"He has aspirations to play for England and in the Premier League and he's got that now.
"I wish him well. Part of me wants to strangle him but you don't want to stop the progress of some individuals.
"Gary feels the next step forward to try to break into the England team is to play in the Premier League, and obviously there is the financial side of things as well."
Meanwhile, Lennon will give Joe Ledley, Charlie Mulgrew and Adam Matthews a run-out on Saturday in the Parkhead friendly against Borussia Monchengladbach as the trio begin their comeback from the injuries that forced them out of the European wins over Cliftonville.