Here is a SQL command based off of the LF server code for the "Total Document Size" entry listing column. It computes the total recycle bin size, including the total sum of all children under recycled folders.

select sum(recycle_bin_sizes.total_recycled_entry_size) as total from
(
 select (case when recycle_bin.orig_name is null then toc.name else recycle_bin.orig_name end) as name, toc.tocid,
 (
  (
   case when toc.edoc_storeid is null
   then 0
   else
    (
    case when toc.edoc_size is null
    then 0
    else toc.edoc_size
    end
    )
   end
  )
  +
  (
   select isnull(sizetemp1.sum1, 0) + isnull(sizetemp2.sum2, 0) + isnull(sizetemp3.sum3, 0) 
   from
   (
    select sum(cast(img_size as bigint)) + sum(cast(txt_size as bigint)) + sum(cast(loc_size as bigint)) as sum1 from doc 
    where pagenum >= 0 and toc.tocid = doc.tocid
   ) sizetemp1,
   (
    select sum(cast(altedoc_size as bigint)) as sum2 from altedoc where altedoc.tocid = toc.tocid
   ) sizetemp2, 
   (
    select isnull(sum(cast(datalength(ann.ann_text) as bigint)), 0) + isnull(sum(cast(ann.attach_size as bigint)),0) + 
    isnull(sum(cast(datalength(ann.bitmap) as bigint)), 0) as sum3
    from ann
    where ann.page_id in 
    (
     select page_id from doc where doc.tocid = toc.tocid and doc.pagenum >= 0
    )
   ) sizetemp3
  )
 ) as total_recycled_entry_size
 from toc
 left join recycle_bin on toc.tocid=recycle_bin.tocid
 where toc_flags & 2048 = 2048) recycle_bin_sizes

This subquery returns the individual sizes of each recycled entry:

 select (case when recycle_bin.orig_name is null then toc.name else recycle_bin.orig_name end) as name, toc.tocid,
 (
  (
   case when toc.edoc_storeid is null
   then 0
   else
    (
    case when toc.edoc_size is null
    then 0
    else toc.edoc_size
    end
    )
   end
  )
  +
  (
   select isnull(sizetemp1.sum1, 0) + isnull(sizetemp2.sum2, 0) + isnull(sizetemp3.sum3, 0) 
   from
   (
    select sum(cast(img_size as bigint)) + sum(cast(txt_size as bigint)) + sum(cast(loc_size as bigint)) as sum1 from doc 
    where pagenum >= 0 and toc.tocid = doc.tocid
   ) sizetemp1,
   (
    select sum(cast(altedoc_size as bigint)) as sum2 from altedoc where altedoc.tocid = toc.tocid
   ) sizetemp2, 
   (
    select isnull(sum(cast(datalength(ann.ann_text) as bigint)), 0) + isnull(sum(cast(ann.attach_size as bigint)),0) + 
    isnull(sum(cast(datalength(ann.bitmap) as bigint)), 0) as sum3
    from ann
    where ann.page_id in 
    (
     select page_id from doc where doc.tocid = toc.tocid and doc.pagenum >= 0
    )
   ) sizetemp3
  )
 ) as total_recycled_entry_size
 from toc
 left join recycle_bin on toc.tocid=recycle_bin.tocid
 where toc_flags & 2048 = 2048

Note: this doesn't consider recycled pages.

To get the size of recycled pages (i.e. pages that were recycled individually, not pages that belong to a recycled document), run the following queries.

Total size of image/text/location/thumbnails:

select sum(cast(img_size as bigint)) + sum(cast(txt_size as bigint)) + sum(cast(loc_size as bigint)) from doc where pagenum < 0

Total size of all annotations:

select isnull(sum(cast(datalength(ann.ann_text) as bigint)), 0) + isnull(sum(cast(ann.attach_size as bigint)),0) + 
isnull(sum(cast(datalength(ann.bitmap) as bigint)), 0)
from ann
where ann.page_id in 
(
 select page_id from doc where doc.pagenum < 0
)