Motherby said in the 1980s replica kits were aimed squarely at children, but had become more popular among adults from the early 90s.
Talking about international kits, he said: “In the 90s you could pick up a replica shirt for about £30, whereas now they’re about £80 to £90, which certainly seems ahead of inflation.
“There are alternatives. I remember when I was a kid there was a real stigma to wearing old shirts – that stigma doesn’t exist any more.
“With the World Cup coming up, people might get kudos for wearing an old, classic shirt.
“You can pick up some bargains and some classic England shirts.”
Motherby started collecting replica shirts after watching his first Hull City game when he was six.
But he said his hobby moved to another level when he realised he could buy genuine shirts worn by players during matches.
“A game can’t happen without two kits that distinguish the sides, and when you realise you can collect those, you think, I’m actually collecting pieces of a club’s history.”