Sooo... I'm taking a raw stab at this... To be perfectly honest from the start: THIS IS NOT A SALE... In the end, my estimation will include the price for renting premium hashrate, adjusted for bad luck, including fees, including rounding margins, some beer money for my time to setup tBTC mining... If you want to have tBTC to OWN, you'd better mine it yourself. As a matter of fact, i'd be happy to give you a cost estimation to help you setup a tBTC node, p2pool and teach you how to setup an ASIC in order to mine on the testnet p2pool node, i can basically guarantee that if you want to OWN a lot of tBTC it'll be cheaper (and more honest) to do it this way.
tBTC is completely worthless, and there is no need to hoard it, the dev's can decide to reset the testnet at any time!!!

The collateral will be high, but it's exactly this: collateral... If you give me the 50 tBTC back, you'll get your collateral back (minus the transaction fees!!!).... If you decide to run, i'll keep the collateral and use it to mine more tBTC to fund my faucet, and i'll end up with some pocketchange aswell.


So here we go... Cost estimation of what it'll cost me if you decide not to repay the loan and i want to get the 50 tBTC back so my faucet doesn't run dry.

Miningrigrentals
This is the cheapest: https://www.miningrigrentals.com/rigs/151500/?currency=BTC
0.00001800 BTC/THASH/DAY * 17 Th = 0.000306 BTC/Day

The formula to estimate the daily income:
(((((Hashrate (hashes/sec) * average block reward * 600 * 65535) / 2^48) / Difficulty) * 6 * 24)

The variables
Hashrate = 17 Th = 17000000000000 Hashes/sec
average block reward = 0.39 tBTC
Difficulty = 10.5M = 10.500.000

The result
((((( 17000000000000  * 0.39  * 600 * 65535) / 2^48) / 10500000) * 6 * 24) = 12.7 tBTC/day
50 tBTC / 12.7 tBTC/day = 3.94 days =~ 4days

The time i'll need to mine 50 tBTC
getting the escrow to release the collateral: 30 minutes
Setting up p2pool on my testnet node: 1 hours
setting up miningrigrentals: 30 minutes
Total: 2 hours @ $25/hour @ 8641 $/BTC = 0.005781

The total costs
4 days of mining  @ 0.000306 BTC/day = 0.001224 BTC to rent the hashrate
I'll have to fund mininrigrentals with a tiny bit extra (10%), since it's not guaranteed that i'll get the cheapest miner: 0.0001224 BTC
Transaction cost (2 inputs, 2 outputs, 10 sat/byte: 0.0000374
Labour cost: 0.005781BTC

Grand total: 0.0071648... So 0.0072 BTC would be acceptable collateral for a 50 tBTC loan.



As said before, the terms are simple:

• 1 month time to repay the 50 tBTC, after exactly 1 month i'll use the collateral to buy hashrate from miningrigrentals, so there'll be no way to get your funds back
• i want 50 tBTC back, you can use the 6 free, working faucets to claim the fees you've spend while testing
• i accept a couple altcoins or bitcoin as collateral, collateral can be helt by a trusted forum escrow if you want to
• all fees are payed by you (escrow fees, transaction fees to move collateral,...)