No idea what you mean by "cheap one".
I won't tell you what we pay for ours, but they don't cost much. In fact, I'll sell you all you want for $3 each, minimum 2, shipping included.
It's a good idea to use a matched pair (same make & model).
Not sure what you mean by "40-2150". If referring to frequencies, what you need is: OTA port: 0-900MHz, Satellite port: 950-2150MHz. OTA can have a lower high limit, a higher low limit (up to 40MHz) and the satellite side can be wider (lower low, higher high).