Just because its cheap, do we assume it's rubbish?

I was just looking through some of my make up and found a few bits from Natural Collection, Collection 2000, Barry M and Sleek (to name a few) and thinking about the price tags, do people that will only shop in places that have extortionate price tags turn their noses up at the cheap stuff?
Take Sleek for example. In recent years Sleek have made such a name for themselves. Their very pigmented eyeshadows have gone down a storm, just take a look at some of the beauty guru's on youtube and you can see that spending a fiver on one of their palettes would be an absolute bargain! Barry M who is loved for their range of nail varnishes (amongst other things, of course) is again, dirt cheap, but then you come to brands who you don't necessarily spend much time looking at because their £1.99 mascara makes you doubtful. Okay, so i love brands like MAC just as much as the next person, but what i dont understand is why people dont jump at these cheap prices? In the past ive paid £2 for a mascara by natural collection, and if i were to compare it to Maybelline's XXL waterproof mascara (the white one end/black other end one) i know the cheap one would win hands down. Okay, so it might not be the best mascara, but why pay £12 when you dont need to? that money you saved could be spent getting something else?
when it comes to things like eyeshadow, i completely understand why people would go for products like MAC over something ridiculously cheap. Pigmentation is obviously really important for a good eyeshadow, and i'd admit that ive gone for both ends to try the difference.
Anyway, what i suppose im trying to say is, these brands, the smaller ones, are alot better than people imagine them to be, and to give that £2 price tag a go, would probably change their minds about some of their products.

Rant over.
Have a good bank holiday weekend guys and dolls. x