There's a very simple way of doing this achievement with a custom mission.
1.
Create population folder in your script folder under tf2 local files. In my case they are in: C:\Program Files (x86)\Steam\steamapps\common\Team Fortress 2\tf\scripts
2. Create a text document in population folder.
Paste script code pasted below this guide in the text file. Save as all files with a name "mvm_mannhattan_Achiev.pop" (Very important)
3. Open TF2 and start a Mannhattan map. To do this, paste this in your console:
map mvm_decoy; hostname "boost"; sv_lan 1; sv_cheats 0; maxplayers 32; tf_mvm_min_players_to_start 1;
4. Start your custom mission with a console command: tf_mvm_popfile "achiev"
5. Start the mission, kill the only bot that spawns. You will collect 30'000 credits (maximum per wave). Mission will end, but before another map starts loading paste the same command in the console from step 4 thus reloading the wave.
6. Repeat last step 1'000'000 / 30'000 = 34 times to get this achievement
As a bonus, with this script it is possible to do:
> Frags to Riches (Following the same instructions will only need to do step 5 once)
> Get Off My Lawn (Following the same instructions will only need to do step 5 once)
> T-1000000
Put in mvm_mannhattan_Achiev.pop file:
#base robot_standard.pop
WaveSchedule
{
StartingCurrency 30000
RespawnWaveTime 1
CanBotsAttackWhileInSpawnRoom no
Advanced 1
Wave
{
StartWaveOutput
{
Target wave_start_relay
Action Trigger
}
DoneOutput
{
Target wave_finished_relay
Action trigger
}
WaveSpawn
{
Where spawnbot
TotalCount 1
MaxActive 1
SpawnCount 1
WaitBeforeStarting 0
WaitBetweenSpawns 0
TotalCurrency 30000
TFBot
{
Class Scout
Skill Normal
Health 1
WeaponRestrictions MeleeOnly
MaxVisionRange 1
}
}
}
}