What do you mean by simple code? If you find some "simple" code out there, let me know. Most code is not "simple"!
I'm not sure if this applies to variants and I haven't tested it at all, but for regular product options that are a price modifier look here:
/common_files/modules/Product_Options/customer_options.tpl
Near line 58:
{if $o.modifier_type ne '%'}
{currency value=$o.price_modifier display_sign=1 plain_text_message=1}
{else}
{$o.price_modifier}%
{/if}
So you could edit this and do some math:
{math equation="price_modifier+current_price" price_modifier=$o.price_modifier current_price=$product.taxed_price format="%.2f" assign=total_variant_price}
{currency value=$total_variant_price plain_text_message=1}
Place the code above in place of:
{currency value=$o.price_modifier display_sign=1 plain_text_message=1}
There might be another way, but this will get the job done I think.
Hope that helps,