Well, there's plenty of cheap wifi phones out there that you can buy unlocked, and have a smartphone with wifi so you can do VOIP to reduce your minute cost. You're just going to loose the coolness factor of not having an iPhone. I suggest you take a closer look at some of the newer iPhone clones from China. I've seen two lately (one with a 200 Mhz processor, the other with a 460 mhz processor), that has alot of neat features like wifi (real) 3G HSPA, front facing camera and a flash on the rear camera all packaged in an iPhone looking package. One runs a proprietary OS, the other runs Windows Mobile.
Take a look at CECT's latest, the F003...
Latest Flying F003 Dual Card Standby Smart Phone with WIFI TV JAVA
It has a 210 Mhz MTK 6235 processor with WiFi and runs about $100-$110 USD.
or...
C6 Smartphone
which runs windows mobile, has wifi, and a 460 Mhz processor and runs win mo apps, and runs about $220 USD.
Both of these phones are pretty cheap, look and "feel" alot like the iPhone, although they are NOT iPhones. You can use these or if you really MUST have an iPhone, and don't want a data plan, then you'll have to buy one direct from Apple for $600 bucks for an 8Gb 3GS (and up). You can then most likely get an account from AT&T w/o a data plan (not 100 percent sure), or T-Mobile for sure. That is if you're in the US.
At the end of the day, you're not going to get a $200 iPhone w/o a data plan. It's just not going to happen. You're either going to pay full price for the phone or live with the contract for 2 years, or, go the knock off route, which seems to be your best bet considering your needs. I still say you should get a data plan because you can't use some of the features when you're not near a hot spot, so it's not as much worth getting if you don't have data connectivity 100 percent of the time, but the choice is yours.