Cheapest (~10-15USD/unit) Wireless Intercom or Simple USB Powered Walkie Talkie Hack

This is a simple hack (just connecting wires) to make a usb powered walkie talkie
i tried this when i was still in elementary school and forgotten about this for years, till recently when my brother ask me to recommend cheap wireless intercom that cost less than 20USD per unit, that can pass thru 3-5 concrete wall for his company.
so i did my researched, and found out it was impossible to get a commercial wireless intercom under 20USD per unit.
wired on was out of the question

my other solutions that fits within the budget was walkie talkie, but all walkie talkies, AFAIK are battery powered.
googled for a usb power ones and found a Motorola MR350R which cost about $30 per unit, $10over the budget

but luckily i remembered my elementary school days.

and tru a simple browsing, it cost:

BOM:

i bought the walkie talkie from the dx.com, but the cable and charger use for this build was my old extra stuff.

I'll use the price from dx.com as a reference anyways

2 walkie talkies ~$26 (2 set pack)
2 usb charger ~$5.32 ($2.66 each)
2 Usb cables ~$2.96 (1.48 each)

TOTAL: $34.38 for set of 2 (postage included) or ~$15 each set

half the price of a Motorola MR350R

price goes down if you buy in bulk.

also, other site(aliexpress) are cheaper. and if i all buy it from them, then the price goes down to ~$10 per set

soo, you can get 3 set per 1 MR350R bought

i just bought it @ dx for the convenience.

soo without further ado, here is a simple guide to hacking it

ATTENTION!!! you know the drill. i do not take any responsibilities and all resposibilities lies with you, the hacker, whatever it causes, including but not limited to, broken devices, electrical shock, fire, explosions, lighting strikes, volcano eruptions, etc..... you get my point.... : p

Step 1: What You Need

PER UNIT or node you'll need :
-. walkie talkie power rated 0.5W-1W (3-4 AA / AAA baterry powered, im using 4*AAA powered ones )
- USB charger, ( i used 5v 500ma for this hack, you might need a higher current if you are using high power walkie talkie)
- usb cable data or powered
- scissors or wire stripper
- solder / tape / conductive glue / anything else to connect and hold wires to the walkie talkies (in mine, i soldered it)

note:
3*AA powered walkie talkies are said to be safe here https://www.instructables.com/answers/Can-my-walky-talkie-take-5-volts/
i didn't try t for Lion, LiPO batt. powered ones, but you can use the same method, with a step down/up voltage regulator and higher current charger if the device is high powered.

Why do i use 4 AA/AAA powered ones? its operational voltage makes connecting to a usb charger simple. a fresh AA battery 1.5++V and goes down to 1V when it almost fully discharge or "emptied". so its operatinal voltage (since it ran in series config) is 1.5V*4 to 1V*4 which is 6V to 4V. power from usb is 5V and it is well within the range.