Guesstimate - How many workers did it took to build the pyramids?

How would you solve this?

This would be my structure (for simplicity just focusing on one pyramid in Egypt)

Number of workers = workers in quarry + workers transporting stones from quarry to pyramid + workers actually building pyramid + other workers

workers in quarry 

workers in quarry = required stones per day /  required workers per stone per day

required stones per day  = required stones total /  time to build pyramid

required stones total = Volume Pyramid / Volume average stone

I would need to estimate 

• Volume Pyramid
• Volume average stone
• time to build pyramid
• required workers per stone per day (this one is tricky, further breakdown??)

workers transporting stones from quarry to pyramid

they were using some kind of sleds to transport stones so

workers transporting stones = required sleds * workers per sled

required sleds  = number of stones per sled per day * required stones per day

number of stones per sled per day = Max number of stones fitting on one sled *  number of rides per sled per day

I would need to estimate 

• Max number of stones fitting on one sled
• number of rides per sled per day
• workers per sled

All of them seem tricky and might require further breakdown.

workers actually building pyramid 

workers actually building pyramid = required stones per day * required workers per stone

I would need to estimate 

• required workers per stone (might requires further breakdown)

Other workers

e.g. planners, other logistics, food, maintenance, etc.

I would just use something like 10-15% of total workers to add.

I feel like this is quite complex even with the assumptions that Im making which could be broke down further. Am I overthinking? Do you like the structure?

Case was asked during an interview of a boutique consultancy and I dont know what additional infos they were providing during the case. I assume they helped a lot otherwise the case is to long  / doesnt provide recruiters so much insights to justify time spend for this case.

thanks!