I suggest highly you talk to Trevor first or laserbee Jerry its 4 am here I'm really tired i grabbed this in a hurry these guys know the every in and out of what you need to know along with ARG, Things,living loud and many other senior forum members I'm sure i missed some sorry ..you will have to buy a LPM laser power meter making one doesn't really seem to be an option .
There's no cheaper method than sending it to a member with a LPM. There's a stickied thread in this section of members willing to do it. Just get in contact with one of them.
That said, there's no way you can accurately tell the power without a LPM. There are countless threads asking "how can I without a LPM", all leading to complete chaos and ending with a LPM or giving up.
Cheapest you will find one is $60 to $80. You can search "diy lpm" and find a few threads that may come close. A better (more accurate) option would be to look at a Laserbee HLPM II. Google it. Its made by a member of this forum and costs I think around $70. You would need to use a neutral density filter though, as it only goes up to 200mw. If you're willing to spend a little bit more, you can get a Bluefan for $125.
So true you are right ....I'm just: a collector of colors and want the rainbow i myself have offered to test in my part of the world, most reasonable if you have only one or two lasers ......but most of us get a lot more