We often forget that the TTP are an umbrella group, it isn't just one agenda at work, it's a whole load of activities going on under the same banner. Likewise, there are numerous sources of funding for the groups.
1) A large amount is collected as "Chanda" from the sympathisers from within Pakistan.
2) Then there are taxes collected from areas under the TTP's control.
3) They receive a lot of "Zakat" from oil rich sheikhs in Arab countries.
4) Some groups receive funding from foreign govt.
5) Some receive support from NGOs and political parties.
Among others.......
Also not to forget the government sanctions from the tax payers money (if that guys exists in Pakistan). I think there was a Pakistani Punjab government's ile exposed when it was shown that 82 Million Pakistani rupees were given to JuD. The minister, Sanaullah at that time had lied saying that this is not the case.
There are also some nice commercial activities happening to fund the jihaadi friends. Sales of some animal hides after the festival slaughter etc. also help raise a lot of funds for Saeed' LeT not to mention the state funds given via the "non-state rogue intelligence agents" etc.