Option Value dropped in 8 days even if the underlying price is the same

There is quite a degree of latitude for market makers to play pricing games in less liquid markets.

The options pricing formulas are a shared reference value, with IV really being closer to a "remainder" in a math formula, used to explain the unexplainable.

The reality is that the market - which includes market makers - simply decide to trade at a certain price. If someone would sell that contract for 90% less and someone would buy that contract for 90% less, that trade of $3 would appear on the chart. If its a good deal then you can consider being the person to buy that contract and sell it at its proper price.

8 days ago, With TSLA at $645 and the 6/21 $1050 call at $47.50, your call's IV was 77.05%.

Today, with TSLA at $645 and the 6/21 $1050 call at $33.25, the IV is 68.95%.

IV fluctuates daily based on news as well as general market conditions. In this case, IV contracted over the past 8 days and therefore so did option premium. You can see a graph of the average implied volatility demonstrating this at Ivolatility (free sign up).

In addition to Bob's (correct) explanation: when you bought them, the news that TSLA gets in the S&P 500 was new, and the sky was the limit for its share price. A lot of people thought it could go very high up, and a lot of (other) people thought it might come down badly.
Now, some days later, a lot of smoke has cleared, and the emotions are not flying that high anymore, so volatility is lower, and therefore, options prices are lower. Maybe tomorrow (which is Dec/18, the last day before the S&P500 inclusion), the fireworks will start again, who knows.

Options trading needs to consider that price depends on volatility, which depends on emotions and news. The formula's predictive power is limited for a thriller like TSLA.