Like anything, it depends. I'd rather not say too much about SG's pricing publicly (since I don't work there and don't speak for them) but it's similar to other agencies in the same market. Ballpark, that means 10k-30k depending on your company's reputation, the scope of work, which people from the agency are on your team and compensation structure.

You don't really pay a whole lot more for higher quality agencies (I could go into theories on why but will save that for another post). Companies almost never hire bad agencies because they can't afford good ones. Far more often it's because they don't know how to find (or identify) the good ones or because the good ones don't want to work with them (it's a big risk to an agency's reputation to take on a bad client).

If anyone wants to email me I'd be happy to go into more detail privately. If you have any general PR questions that aren't agency-specific (hiring agencies, hiring consultants, how PR can be successful, etc), I'd be happy to answer those publicly.

Edit: In case anyone is curious, other YC companies SG has worked with are Xobni (I worked on this account), Scribd (I worked on this account too), Loopt, Zumodrive and maybe others I'm forgetting.

Usually a retainer at $10K+ a month, and usually more for a launch like this depending on the number of resources you need.

Some smaller firms may take a lower retainer, take stock or defer payments. It all depends - but ~$10k is average.

People have different opinions, but I believe that with a startup, especially in the early years, the CEO has to be actively involved in PR. You should build relationships with bloggers who cover your space and/or have an interest in your company. If you do this well, it is worth more than any amount of money you will spend on a PR agency (it will also give your company a more authentic voice, rather than a dozen re-bloggers regurgitating your releases).

In the case of Blekko, their PR agency would have contacted all the media outlets, setup the briefing times, but together the release and then followed up with each reporter. There is a lot that can go wrong, and it usually does. The blekko PR team should have known that with so many outlets covering this launch, the chances of somebody breaking the embargo and pissing off the other outlets was near 100%.

I sat through tons of briefings at TC, and when a blogger asks who else is covering the launch, you can gauge pretty quickly if the embargo is going to be broken or not. It is so frustrating when an embargo is broken, because you put the work in only for it to be wasted - and there are no repercussions for anybody breaking an embargo, which is why TC simply threw them out. It is a complicated world with a lot of internal industry politics between outlets, firms and companies and a good PR firm should be able to guide you through that (but most don't).

If you have a product launch coming up and you are trying to decide if you need PR or not, try emailing one or two bloggers now and let them know you have a launch coming up in 2-3 weeks (or whenever) and see the reaction. If you get nothing, you might need help with your messaging (the attention span of a blogger with an inbound cold email is around 7 seconds - so you need to be snappy). If you get interest, then handle it yourself and get to know the industry, which will be very important for you in the long-term (and something you should do even if you do have PR).

You should also be building your own profile with the company blog and perhaps your own personal blog. If you become a source of stories or links for a blogger you will find it easier to get your own stories out (quid pro quo).

If you need some tips feel free to email me (email in profile) - I both spent a long time at TC and in startups before that, and startup again now.