A step 1's prize pool consists of two step 1 entries and two step 2 entries. The price of a step 1 entry is $3 and the price of a step 2 entry is $10, but these are not the values of the entries (making no assumptions about the relative skill levels of the players), the value is less. If these were the values, the prize pool would be $26, which means that the value of the step 1 entry would be $26... except it can't even be that, because we now know that the step 1 entry must be worth no more than $2.60, etc.
The same is true of all the steps, bar step 6 which only pays cash and is easy to work out the (unbiased) value of. You can create a system of linear equations to represent the values of each step entry (or the prize pools if you like, or the difference between the face value and actual value, which I call the effective fee).
0 = -8S_1 + 2S_2
0 = 3S_1 - 8S_2 + 2S_3
0 = 3S_2 - 9S_3 + 3S_4
0 = 2S_2 + S_3 - 9S_4 + 3S_5
-$940 = 2S_3 + 2S_4 - 8S_5
...you can write it other ways, but this is closest to the matrix form which can be inputted into automatic solvers, not being a toy problem this is a tad too tricky to do by hand. Such a solver is at http://wims.unice.fr/wims/en_tool~linear~linsolver.en.html (er, that one actually has a few modes of operation, but I hadn't googled before writing out the system).
The solution given is:
S_1 = $47/39 ~= $1.21 (face value is $3)
S_2 = $188/39 ~= $4.82 (face value is $10)
S_3 = $1363/78 ~= $17.47 (face value is $30)
S_4 = $3713/78 ~= $47.60 (face value is $70)
S_5 = $1739/13 ~= $133.77 (face value is $170)
Obviously it's not this bad if you have a solid edge in every level, as you're more likely to finish in the higher places and the entries are thus worth more to you, but one thing is absolutely clear: for anyone else, the lower steps are an appalling deal and the variance is also hideous. Quite singularly unsuitable for practice.
Get cash for your party points instead, 300 pp for a step 1 entry is still just 1 cent per point (on the face value!) which is what you get when cashing them in anyway.