Personally I like to keep the walk-in price high - because that then helps to establish the "value". Discounts then look that much better - because they are compared against that relatively high initial price.
Our walk-in price is $35. But with pretty good regularity, we run a special of "Buy 3, get 1 free" ($105) or 4/$99.99. That is actually the most common package we sell on that bed. It is a better discount to buy the 10 or 20 session packages -- but not everyone has several hundred dollars they want to fork over at once. So they buy those 4 packs time after time after time....
Now -- with NEW customers, we let them trade in one of their "3 Free Tans" to try the Matrix for just $15. It is the cheapest they will EVER pay to use that bed!! MOST do it at least once when they are new - sometimes all 3 times. So we hook them from the first day in the salon!
I would keep your price up at $29 - even $32. Then, for ANYONE that has never tried it -- even if they are a current customer -- let them "try" it ONE time -- for $15. Who doesn't want to try the very best thing you have for 50% off??
At $32-35 walkin --- it is much easier to show the "value" of 5/$110 or 10/$200. When $24 is your walk-in --- doesn't seem like that much of a savings to buy in bulk.
And THEN - you could do a 3/$75 or 4/$99 -- and it would look like a DEAL - rather than normal pricing.
It's all about setting "perceived value"!
