It depends on the business. $MAJORWIRELESSOPERATOR on accessory sales has obscene margins (like 1000%). Things like minutes are skinny with gross margins of 60-100%. There are costs so if you're playing the LCR game you're likely making 4-10% net margin.

It all depends on volume and cost to deliver. Some of the biggest providers have the highest costs to deliver service.

Does that help?

Edit: for example, a hosted PBX provider, pricing at $35 all inclusive per seat, should have gross margins north of 150% and net margins above 40%, assuming at least 10,000 seats. There are, of course, huge variations because of management style, frugality and a myriad of other factors, but there's money to be made.

The easiest money in telecom, with the highest margins, are the Analytics, billing and operations tools (of which there are many but finding quality ones is a YMMV proposition).