Congrats to avast! on the current avast! 5 Pro pricing for multiple PCs.
Like others, I been using 4.x Pro on main system, and 4.x Home on my other two systems due to avast!'s Pro license pricing for multiple PCs really did not offer much of a discount. Price of avast!'s 4.8 Pro licenses for three PCs was close to price of the major security suites (NIS, KIS, etc.) for 3-PCs.
Out of curiosity I just checked the current pricing for PRO and AIS. Pro current pricing (USD): 1-year/1-PC $39.95; 1-year/3-PCs $54.95.
With the older avast! Pro multiple license pricing method 1-year/3-PCs would be $83.99 +/- depending upon the discount given for multiple license purchase; e.g., 3 x $39.95 = $119.85 less $35.96 [30% discount] = $83.99