Nick,
Foot ascenders ARE worth every penny you pay for them.
Look at the long term benefits. I have no clue how old you are or how long you've been climbing. If you want to have a long, healthy career with as few worn out body parts when you get older make use of good techniques and tools.
Too often arbos get caught at the crossroads of traditional and progressive [my terms, we've discussed their meanings in the past...check the archives] climbing styles and they've felt that there is some sort of demotion or dilution of the craft by using rope tools. Stop and think about the value of tools. How much did it cost to get you in front of a keyboard and connected to TreeBuzz? Would you go back to rotary dial phones or snail mail to try and learn? It works...but how well?
Many climbers have had conversion experiences when they get their first back ache or shoulder bruise. We realize our vulnerability and project out any number of years then realize that it's time to change our ways. Others just plod ahead and continue to wear themselves out.
Think of your joints as paperclips. How hard is it to break a paper clip if you give it a good wrenching? Can you also cycle it many times without breaking it? Get the metaphor?
All climbers should know how to safely climb using nothing but a single rope...no biners, snaps or Unicenders [that would be a tough one to give up

]. Set the rope using a monkey fist and tie a three loop bowline and heft yourself into the tree. One day you'll find yourself with just a rope and the opportunity to make a few bucks. There is no way that I would start a new climber at that level but it is a right of passage in mastering tree climbing to be able to climb with just a rope. Then, learn the progressive skills too. When you can afford a tool, get one. The gang here at TB are brutal when it comes to new gear. They'll dissect the performance and value and hopefully not leave you too confused.
By saving the wear and tear on your body when you're young you'll be healthy when a few decades of climbing pass under your boots.