Its math time!
For a limited time only, booster packs contain 10,000 gems.
The booster pack has 7 upgrades in them which can be found
here and costs $5 USD. Now if we split the money between each upgrade or item in the pack it would cost ~$1.4 USD per item/upgrade (for a limited time only)
Now the average RP money to cash is about $0.000001 per ingame dollar meaning its $1 USD per every in-game million, making 10,000 gems cost one million and four hundred thousand in-game.
The Gluon gun is 10x that as it contains 100,000 gems making it worth 14 Million in game dollars and $14 USD to purchase with real money.