As others have indicated, there are many ins and outs. The TX/RX pair you linked to should work, so you could have everything you need for testing two-way transmission--2 08M2s, 2 TX, 2 RX for under $7US (with this gear, your RX will be "blocking" with 2-way RX, so you can't do something else while waiting to receive). Add two nkm2401s and use 2 14M2s and you should be around $10US, with non-blocking tx/rx.
If you go this route, make sure you have it working wired before you insert the wireless modules.