I couldn't help but angry as I knew she had eaten the cake that costed me twenty dollars. soa natural?

It was the past tense, but it is an irregular verb, that means it is a little bit different than the rest. I will show how to conjugate the "to cost" verb:
Conjugation of 'To Cost'

Base Form: Cost
Past Simple: Cost
Past Participle: Cost
3rd Person Singular: Costs
Present Participle/Gerund: costing.

I will give you a list of other verbs that are irregular that might give you trouble, that follow this same pattern and you have to be careful with:
I will show you each verb in a)Base Form b)Past Simple c)Past Participle
1. a)Bet b)Bet c)Bet
2. a)Bid b)Bid c)Bid
3. a)Broadcast b)Broadcast/Broadcasted c)Broadcast/Broadcasted
4. a)Burst b)Burst c)Burst
5. a)Bust b)Bust c)Bust
6. a)Cast b)Cast c)Cast
7. a)Cut b)Cut c)Cut
8. a)Fit b)Fit/Fitted c)Fit/Fitted
9. Forecast b)Forecast/Forecasted c)Forecast/Forecasted
10. a)Hit b)Hit c)Hit
11. a)Hurt b)Hurt c)Hurt
12. a)Input b)Input/Inputted c)Input/Inputted
13. a)Knit b)Knit/Knitted c)Knit/Knitted
14. a)Let b)Let c)Let
15. a)Miswed b)Miswed/Miswedded c)Miswed/Miswedded
16. a)Preset b)Preset c)Preset
17. a)Put b)Put c)Put
18. a)Quit b)Quit c)Quit
19. a)Read b)Read c)Read
20. a)Rid b)Rid/Ridded c)Rid/Ridded
21. a)Set b)Set c)Set
22. a)Shed b)Shed c)Shed
23. a)Shut b)Shut c)Shut
24. a)Slit b)Slit c)Slit
25. a)Split b)Split c)Split
26. a)Spread b)Spread c)Spread
27. a)Sublet b)Sublet c)Sublet
28 a)Sweat b)Sweat/Sweated c)Sweat/Sweated
29. a)Thrust b)Thrust c)Thrust
30. a)Upset b)Upset c)Upset
31. a)Wed b)Wed/Wedded c)Wed/Wedded

These are some maybe there are more, but I hope this helps you.