The caveat to this is that if you're renting a studio to visiting mixers they will probably want a big waves bundle. If not, don't worry.
The good news is that Waves, and most other plug in manufacturers have cottoned onto the fact that we're just not going to spend a fortune on each plug in. If there's a particular plug in you want, check the eBay resellers and check Waves's website. You'll probably find it quite affordable.
There are two main areas where all plug ins represent a compromise. Compression is still not as good as hardware. We can speculate for hours about why this might be but the long and the short of it is that plug ins tend to be very good for controlling level, but their ability to shape a sound, to have the sound of 'compression' is still limited. It all looks right on paper but the attack just seems odd. I've done quite a bit of comparison with the latest greatest plug ins and the problem is still there. Although it's better than it was a few years back. I expect leaps and bounds will come in time. The other area is distortion. And perhaps that's what doesn't quite compute in the compression world. Perhaps the way an analogue compressor distorts around its onset of attack provides the bite that's missing...but anyway...distortion is not right.
Now, I'm not saying that you shouldn't use those plug ins, you will need to and should. But just be aware of their limitations and trust what you hear, not what you read in the marketing blurb.