It's easy to tell you what's different between $60 and $150. If you want a lady who has even a little class, takes reasonable care of herself, and is interested in providing quality service; you won't find that for $60.
Simply put, if a woman is willing to give up her intimacy to a complete stranger for only $60 then it probably means she's desperate for the cash. If the lady is that desperate, it's quite likely that she does not have the motivation to provide unrushed quality service or take proper hygienic care of herself or her customers. I don't do street pick-ups but, from what I've heard, I doubt you could even find FS from any but the most desperate crack-addicted street walkers in this city. I'm assuming that's not the experience you're looking for.
Any lady who has decent looks, is clean, reliable, and can keep an appointment can easily command $200 for an hour in the current market. You really want to consider why a provider is prepared to significantly undersell herself and then decide if you're willing to take on that baggage for a bargain release.
If you are a first-time to the hobby, you've done well to check out TERB before taking the plunge. Look for reviews of a provider that fits your personal taste and who has consistently good feedback in the review section. You don't want your first time to be a gamble. There are some reliable and quality ladies available who are well and consistently reviewed. Once you've had some experience, you can start experimenting and taking one for the team.
Unless you get off on the idea of a dirty, risky, skanky, encounter (it's fine if you do, but most on TERB don't), the $60 option is not for you. At $60 a go she's unlikely to have the money to work from a decent hotel so you're either going to a (not so private) dive of her choosing or risking bringing her into your own space. be careful.
The real question is, what's the difference between $200 and $400 (assuming for the hour). The answer to that question is much more subjective and there have been countless debates on that topic on this board (perhaps that's why you have seen some smart-ass remarks). It has to do with supply and demand, marketing, PR, and a whole lot of other factors.
keep us posted on what you decide to do.