Back when I was a kid, I used to get lots of 1/18 models, usually Burago and Maisto ones. These were always around £15-20 but there's not really as much of that now. I remember they were other makes around that level too like UT and Gate and if you found the right sales you could find even the really good AutoArt stuff for about £20-30 (I still regret not getting the Range Rover they did). Now it's all much too expensive for me to collect them. And I liked my opening bits.

The resin models all look good and the way the market is they can do lower-interest pieces profitably (cf the K70) when back when I bought 1/18s the ranges were mostly made up of Ferrari, Lamborghini etc.