In Stripe's Tier and Plan object there are two versions of amount fields - amount (integer) and amount_decimal. Stripe allows for fractions of cents as an amount (ex. USD $0.015 etc.) 

When fivetran ETLs an amount with a partial cent - the value returns NULL (source $0.015 = target NULL) 

Please add the following fields into the connection:

• stripe.tier.flat_amount_decimal
• stripe.tier.unit_amount_decimal
• stripe.plan.amount_decimal

https://stripe.com/docs/api/plans
(This relates to support case 165011)