I'm just starting minning, but I'm very confused with the prices of the S7. I hope that someone give me a hand  with this. I see prices of S7 batch 1,2, etc to 1200 - 1000 $. But in the official page the S7 batch 17 is 450 $. I just don't get it what's the difference with batch 1 and batch 17. And with the halvening right in the corner. Should I wait for the next generation of minners? Or go for the current S7.
okay  prices drop on gear .
so batch 1 was high price
 batch 17 much lower
look at this chart
https://bitcoinwisdom.com/bitcoin/difficultyDifficulty History
Date   Difficulty   Change   Hash Rate
May 11 2016   194,254,820,283   8.73%   1,390,530,167 GH/s   Batch 17 around this date so 194,254,000,000  Much harder to make a block
Apr 28 2016   178,659,257,773   -0.01%   1,278,892,782 GH/s
Apr 14 2016   178,678,307,672   7.09%   1,279,029,147 GH/s
Apr 01 2016   166,851,513,283   0.82%   1,194,369,655 GH/s
Mar 18 2016   165,496,835,118   4.46%   1,184,672,491 GH/s
Mar 04 2016   158,427,203,767   -3.10%   1,134,066,098 GH/s
Feb 19 2016   163,491,654,909   13.44%   1,170,318,852 GH/s
Feb 07 2016   144,116,447,847   20.06%   1,031,625,717 GH/s
Jan 26 2016   120,033,340,651   5.89%   859,232,121 GH/s
Jan 13 2016   113,354,299,801   9.12%   811,421,684 GH/s
Dec 31 2015   103,880,340,815   11.16%   743,604,444 GH/s
Dec 18 2015   93,448,670,796         18.14%   668,931,642 GH/s
Dec 06 2015   79,102,380,900          8.77%   566,236,898 GH/s
Nov 24 2015   72,722,780,643         10.44%   520,569,941 GH/s
Nov 11 2015   65,848,255,180        5.77%   471,360,171 GH/s
Oct 29 2015   62,253,982,450          2.25%   445,631,364 GH/s
Oct 15 2015   60,883,825,480         0.12%   435,823,399 GH/s
Oct 01 2015   60,813,224,039         2.49%   435,318,014 GH/s       Batch 1 around this date   so  60,000,000,000   Much easier to make a block.
this changes price.
all you need to consider buying gear is to know what your power cost is.
at the moment it is hard to earn money if your post cost is more then 8 cents