I've had V02 max testing, and it didn't help in my training one iota. Knowing your VO2 max is good for barroom bragging (or in my case self loaving)

Knowing your Lactate Threshold Heart Rate, and power at LTHR ( essentially your functional threshold power) on the other hand is valuable, in that you can use it to set up a Heart rate based training program. In fact the last time I had testing done in a lab, my COach didn't even bother to do the V02 max part.

Also, I've found, particularly with a power meter, that you can get all the data you need from field testing. Moreover, the field testing data is probably more useful because its easier to repeat.

The last time I did test in the Lab, my LTHR, and power were almost identical to what a field test predicted. Thus, since I got a power meter, I don't test in the lab anymore.

I'd save my money toward the purchase of a power meter.