I tend to buy predominantly physical, although with the prominence of DRM on PC nowadays, I don't buy all that many physical PC games nowadays. I usually give preference to the PS3 or Wii U version. An exception is for download-only titles, where I'll often buy it on PC because buying it from the Nintendo eShop or PSN makes little difference. What I have been doing of late is buying games on PC that I already have on consoles for a few dollars, so that I have a version with no online DRM AND the better PC version (Mortal Kombat, Deadpool, House of the Dead: Overkill).
The vast majority of my PC purchases are bundles and reduced-price GOG games, although I will be buying The Witcher 3 full-price on disc. The last time I bought a game at full-price from GOG was The Chaos Engine. I have almost never bought a game for more than $10 as a digital download (one exception: Minecraft), and those have mostly been games that I've actually wanted. I generally don't pay much more than $4 for "curiosities".
When it comes to DRM-free, physical releases, the limit is €60 for games I really want and €30 for curiosities.