No, it's not worth buying. As redzaku mentioned - buy cheap, buy twice. Except hopefully the second time, you're smart enough to not buy cheap.
For M9s (and most GBBPs), the minimum that you'll want is a KJW. You can find them for $150-$200 in most Canadian stores. If you have the extra money to spend, it's worth buying a KWA or Tokyo Marui.
If "over $100 isn't that cheap", then don't waste it on WEs or anything below that. You'll just be throwing money into the wind. Stick to KJW, KWA, or TM, and you'll have a much better time.
* KJWs are TM clones, made in China/Taiwan - they are parts-compatible with TMs, but don't have the quality of TMs. They are available in full metal, or smoked plastic lower receiver.
* KWAs are NOT TM clones, but KWA does make their replacement parts readily available directly through KWA. They're full metal, have the correct dimensions, and have a functioning decocker. They're generally considered on par - or in some cases, better than - a TM.
* TMs are considered the highest quality, for most pistol models. They're accurate, they're responsive, and they're durable. They're also plastic, and have a lower FPS (both due to Japanese law), and are very expensive, so that turns off a lot of newbies.
TM has produced two main versions of the M9:
Their first M9 version is one of their oldest models, and has a fixed hop up, and no functional decocker. That is what the KJW is based on, though the KJW has an adjustable hop up. Avoid this first version, and go KJW instead, if you so wish.
The newer M9 - the M9A1 - was released a couple years ago, and generally addresses the above problems. It feels better than the first version (weight distribution), has an adjustable hop, and a functional decocker. It still takes the first version's mags.
Things to note:
* KJW and TM are compatible, and so are their mags. TM mags are higher quality, and will develop a leak less often than a KJW would. Leaks are fairly simple to repair though.
DO NOT run CO2 in a non-reinforced TM. TMs were built to run on duster (and can handle green gas), but that's it. Again, Japanese law says they can only shoot 1 joule, and shouldn't be modifiable to shoot beyond that.
* KSC and KWA are "essentially" the same company. They are two different companies, serving two different markets, with sometimes slightly different guns, but in most cases they're referred to interchangeably. In this case, a KSC and a KWA M9 are the same thing. You're more likely to run into a pistol labelled KWA than a KSC in Canada, though.
* WE/HK3P pistols are also TM compatible, but absolute shit.
* Don't waste money on anything lower.
Edit: Post #9 in this thread here, is a pretty good overview: M9 - which one is best? - boards.ie