I am working with products that is currently using Siemens and Wavecom modules. We have been using Ericsson and Nokia modules. We have evaluated a number of other modules too, and the selected module might quickly change if we get a specific requirement or a manufacturer happens to introduce a new module.

But in the general case, it really doesn't matter so much which manufacturer you select. The prices and performances are reasonably similar until you need larger volumes where every EUR/USD/SEK/... will matter. Since new modules are released all the time, it may be advantageous to switch if you get a new feature needed for a specific market, or you get a very tempting 10k price.

In this case I just took the BenQ as an example by being a "stupid end user" and selected ELFA (Nordic component supplier represented in a number of other European countries too) and picked the first GSM/GPRS module that did show up. It was an example of a low-cost entry-level module. Most manufacturers have them. In the case of the BenQ, ELFA would supply the technical support - either directly or through BenQ.

I selected a supplier who typically have modules in stock. ELFA is not known to be cheap for low-quantity deliveries, so unless you are talking about k volumes, you may be better off using the phone and call around.

But to continue on the same track. The M23G was an entry-level tripple-bander to allow it to work in US. But I expect you should be able to find the coolest high-end quad-band modules (any manufacturer) for no more than €80-100 in single quantity. When you reach these prices, you can normally run scripts or even compile your own C programs for use in the modules, and they may have SPI, I2C, ... for directly controlling your device instead of being a slave module just responsible for the bandwidth.

If a module is too complicated to use for a one-off project, the next step up is still not (and never will be) a normal mobile phone. It is instead RS232-controlled (or for 3G modules normally USB-controlled) plastic boxes intended to be built into customer producs instead of being connected to an end-user PC.

The free-standing modem CEP GT864 (German) is quad-band with RS232 port with integrated AT-driven TCP/IP stack. Yours for €159 for a single unit. And this was just a quick example too - no time spent on finding the best modem or the cheapest modem. Most probably, you could find the cheapest free-standing modems at around €100, which is way cheaper than your $350.

$350 is a not too uncommon price for an evaluation kit with a module, PCB with module connector, RS232/USB, a transformer, a CD with all documentation and sample code/test programs, ...