Shopping Mad

So I went into a city outlet of a national health and beauty retailer. A staff member greeted me brightly at the door. "Hi! Welcome to national health and beauty retailer. Can I help you with anything today?" 

"Uhh...I was just after some nail scissors."

So she walked me over to a display of such implements and took a packet off the shelf. "We have these ones, they're twelve dollars. Was that what you were after?"

Tired and grumpy, and expecting a pair of nail scissors to cost about four bucks, I replied with possibly less grace than was warranted, "not for twelve dollars I'm not."

We looked at each other for several uncomfortable seconds.

We then looked at each other for several even more uncomfortable seconds.

I spoke first. "This is why it's for the best if I do my shopping on my own", I said before me and my long toe nails made our exit. 

Am I the only one who just fucking hates this? I know from working in retail that a few customers will head straight for the service counter and want to be walked through the entire transaction, but most people are happy to figure it out themselves. Why can't shop staff just leave us alone? I'm not talking about small and specialised businesses here, but the large retailers who seem to think customer service involves herding you around like sheep. Or they have staff randomly standing around the store, and you have to awkwardly respond to their greetings as you consider your purchases. 

As someone who is picky, cranky and broke, I need to do my shopping alone. If your stock is too expensive, or not what I was after, or just a bit shit, I shouldn't be forced to explain it to you like the problem is on my end. But how do I get staff to leave me alone? I've tried various tactics - headphones, looking like I'm about to burst into tears - but it doesn't work. And it's worse now that I'm well into my thirties, which makes me look, to a 19 year old, like I'm middle aged. Help.