Very interesting, got some HOPE RF with SX1278 chip, but I never tested them due to the lack of LoraWAN implementation @ 433MHZ, nor LMIC and TTN gateway have the 433MHz option/settings in the code. May be we'll see them sooner.
Anyway $2.61 for SX1278 (may be same as RFM98) is incredibly low because you can't find any RFM98 below $7 without case and antenna connector
Here are Semtech specs
SX1276 137-1020 MHz -111 to -148 dBm
SX1277 137-1020 MHz -111 to -139 dBm
SX1278 137-525 MHz -111 to -148 dBm
SX1279 137-960 MHz -111 to -148 dBm
and Hope RF ones
RFM95W 868/915 MHz -111 to -148 dBm may be SX1276 chip ?
RFM96W 433/470 MHz -111 to -148 dBm may be SX1278 chip ?
RFM98W 433/470 MHz- 111 to -148 dBm may be SX1278 chip ?
Anyway I never understood the difference between RFM96 and RFM98, even sellers don't know...if anyone has an idea, let me know!