"It's nothing like the valuation of Torres, Keane, Pavlyuchenko, Adebayor. So put these things in perspective.
"It's £8m with a bit more if he does well - how big a transfer fee is that in today's market? What sort of players are being transferred for that sort of money? I mean how much was Pavlyuchenko?
"AJ represents very good value for the money we paid. He has proven he can do the job at Premier league level for years."
Johnson, who joined from Everton this summer, took his time settling in at Craven Cottage. But he has bagged four goals in the last four games.
Hodgson added: "It wasn't a gamble to buy a player with such a proven track record.
"Players of quality don't lose that quality overnight after going two or three games without scoring a goal.
"It wasn't surprising he didn't score goals in his first few matches but we had no doubts that he would score goals, he would work hard and he would help the team.
"But it's not just a question of how many goals he's going to get, it's about how the team will do with him playing.
"To be frank, it's not going to be a great deal of use if Johnson scores 20 goals this season, is the league's top scorer and we're relegated.
"I would much rather end up with Johnson on five goals and Fulham in mid-table."