No question, visualization is an effective method for reinforcing tennis strokes but professional video analysis can be expensive.
For those who want a look but can't afford packages being offered at clubs and training centers, Ultimate Pro Compare offers VOTSA (Video Overlay Tennis and Sports Analysis), an accessible and affordable way to analyze your tennis strokes. Analysis per shot/stroke starts at $20.
Here's how it works:
Peruse the strokes of a number of touring pros Ultimate Pro Compare has hosted on the site. Pick a pro and shot you want to compare with and then upload a video of you making the same shot ( f. ex. a serve or cross court forehand). VOTSA compares your strokes to the pros by placing them side by side for comparison.
That's level one. Take it a step farther and for $50 you get a complete stick figure overlay with swing path and eye contact analysis (as illustrated above in screen grab). The stick figure is your selected pro's exact position at every point during your stroke. You will see, for example, if your racquet position before point of contact is as close to the pros as you think. Pro strokes on the site also include those of: Kevin Anderson, Jeremy Chardy, Mark Knowles, Dmitry Tursunov, Donald Young, Fernando Verdasco, Mahesh Bhupathi (cousin of VOTSA's creator), Agnes Szavay, Nadia Petrova, Alize Cornet, Sorana Cirstea and more.

Well so for 50 dollars you get this comparison with a bunch of strange named players (well some of them).

I can do all this in a normal 35€ lesson - but of course you have to be here for it to work.

Click on the picture below to go to the see and have a look.