So the Google Play Edition Galaxy S4 is for sale now, but if you want the Samsung version with all the custom features? Well, you can get it on the cheap today. The international Galaxy S4 is on eBay Daily Deals again, and it's come down in price since last time. Now it's only $549.99 with free shipping, down from $575 last time. The Google Play version is $100 more.
This is the unlocked i9500 with 16GB of storage and the Samsung Exynos 5 Octa ARM chip. There won't be support for 4G LTE, but it has HSPA+ 850 / 900 / 1900 / 2100. T-Mobile support is going to be a little sketchy unless you're in one of the 850MHz re-farmed areas. No CDMA, though.
Keep in mind you lose a lot of storage to the Samsung software on the 16GB model. Might be a good idea to pick up a microSD card at the same time.