I have used recently the tool sloccount on the source code of the latest stable version of Open Journal Systems (OJS 2.4.5). The result is given below. It suggests that the development from scratch of such a software is a non trivial expensive task: 18M USD.
SLOC Directory SLOC-by-Language (Sorted) 193863 lib php=115818,xml=77854,sh=160,perl=31 120061 plugins xml=61444,php=58126,sh=453,perl=38 86143 locale xml=86143 31919 classes php=31919 21965 help xml=21965 21619 rt xml=21619 14607 pages php=14607 5198 dbscripts xml=5198 472 tools php=472 419 registry xml=419 373 controllers php=373 1 top_dir php=1 0 cache (none) 0 docs (none) 0 js (none) 0 public (none) 0 styles (none) 0 templates (none) Totals grouped by language (dominant language first): xml: 274642 (55.30%) php: 221316 (44.56%) sh: 613 (0.12%) perl: 69 (0.01%) Total Physical Source Lines of Code (SLOC) = 496,640 Development Effort Estimate, Person-Years (Person-Months) = 135.48 (1,625.75) (Basic COCOMO model, Person-Months = 2.4 * (KSLOC**1.05)) Schedule Estimate, Years (Months) = 3.46 (41.51) (Basic COCOMO model, Months = 2.5 * (person-months**0.38)) Estimated Average Number of Developers (Effort/Schedule) = 39.17 Total Estimated Cost to Develop = $ 18,301,446 (average salary = $56,286/year, overhead = 2.40). SLOCCount, Copyright (C) 2001-2004 David A. Wheeler SLOCCount is Open Source Software/Free Software, licensed under the GNU GPL. SLOCCount comes with ABSOLUTELY NO WARRANTY, and you are welcome to redistribute it under certain conditions as specified by the GNU GPL license; see the documentation for details. Please credit this data as "generated using David A. Wheeler's 'SLOCCount'."
The source code of common operating systems kernels (Microsoft Windows, Apple Mac OS, Linux, etc) has dozens of millions of lines of code, mostly in C and in Assembler while for OJS it is approximately half a million of lines of code in PHP and in XML.