In the world of sponsorships there are generally two kinds, primary licenses(which you can distribute) and site-locks(which only work on your site). While primary licenses are useful on just about any arcade site, site-locks have very limited use and should only be purchased on certain types of sites.
Basically site-locks are only good for retaining traffic and have almost zero marketing or promotional value – which is what most sites need. Because of that reason, most sites(like 99% of sites) have very little use for them. The only sites that would have reason to buy a site-lock at any price are the big sites. If you run a small or medium sized arcade site(less than 300,000 page-views a day), then you should not buy site-locks, no matter the price because even if they are under $100, it is most likely not worth it. If you go the site-lock route, it only makes sense if all your games are site-locks since a site with some site-locks games and others not still gives traffic away to other sites and would make no sense and be a waste of money. This confines smaller sites in another way. Some really good games(like a lot of the stuff that armorgames.com puts out) are sponsored on an exclusive license or are made in-house so site-locks are not available for these games. Therefore, you will not be able to put these games on your site which could deny you a decent amount of traffic from SEO.
You might think that sites like Armorgames.com or Andkon.com are successful by doing only site-locks and got big that way, but that is also not the truth. Both Armor Games and Andkon were already huge before they started buying site-locks. Neither site has really grown at all because of buying site-lock licenses. Since site-locks have no promotional value, they actually do not bring in any new traffic. They just prevent people from clicking on logos within the game and leaving your site. This contributes only a small amount to the overall bounce rate for a site. Armor games grew because it got into the game early and sponsors on primary or exclusive licenses to attract new traffic. It was already an industry leader before it started buying site-locks. Andkon sprung up suddenly and grew huge because of a massive paid ad campaign a few years ago where almost every single Ad on a gaming site was for Andkon.com. There really isn’t any arcade that grew popular or big because of site-lock buys so it is not good way to initially gain popularity.
If your site is a huge site already, don’t buy site-locks as they are not a good investment. Instead spend the money on directory listings, primary licenses, and even site design. You will get a much better return on investment if you do so.