From my quick math, a 1% market gain over the next year on $200k would be more than the 10% I will gain on the $10k on its own. Am I thinking about this correctly?
No.
The only way it would make sense not to take up the offer is if there is a some lock in period that is too long for you, or if you can be sure that your porfolio will perform >10% in the next year.
Currently you have a $190k portfolio and $10k to add somewhere.
If you place the $10k in the SDP it will be $11,038.12 after 12 months having compounded at 2.5% each quarter
Your remaining $190k growing at 1% over 12 months would be: $191,900
This would make a total of:
$191,900
+
$11,038
=
$202,938
If you put the $10k into your portfolio it would be $200k, if this grew at 1% then it would be worth: $202,000
A net loss of $938.
Even if we imagine the portfolio grows at 9.5% in the next 12 months:
$190k growing at 9.5% =
$208,050
+ SDP Return ($11,038)
= $219,088
Adding the $10k to your portfolio:
$200k growing at 9.5%
=$219,000
A net loss of $88.
The only way it make sense not to use the SDP, everything else being equal, is if your portfolio will gain more than 10% in the next 12 months.
This is unlikely.