I now have a monthly limit I won't go over. In the past, I've treated the limit as a target, and wasted money on punts for the sake of it near the end of the month if I was under limit. Hopefully I won't do that again.
On individual punts, I don't really have a limit, but do look for value. Anyone over £120 ph is likely to be a one off for me, and would need to be something special to be worth it. 2 of my top 5 punts were £70ph and £80ph.
You could always do a half hour punt if you don't want to stretch to £130, or ask for a 45 min price.