How so? Cheapest SSD I can source locally a reasonable NZ$143 - smallest available is currently 120GB, meanwhile I can get a 500GB HDD from the same supplier for oh NZ$75 so sorry, even with that back-flip SSDs are not available for HDD money - and if they want to keep selling them HDD makers will have to ensure there IS a good like for like differential because of the speed difference.
That is also without having to buy an external HDD and/or caddy to enable the 380GB drop in internal capacity through installed an SSD...so it would actually cost (assuming you have a 500GB internal and re-use it in a caddy), NZ$143+25=NZ$168 when an HDD could be bought for NZ$75...in OP's case he may have a terminal HDD so he would need to spend NX$143+25+75=
NZ$243 instead of NZ$75...
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LOL yep

see my maths example, SSD is still 3x the cost of an HDD in the OP's situation...even if you give up the onboard space...